sysfs: Fix several clang-tidy issues

* cppcoreguidelines-avoid-c-arrays
* cppcoreguidelines-pro-bounds-array-to-pointer-decay
* readability-identifier-naming

```
../sysfs.hpp:45:28: error: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays,-warnings-as-errors]
    static constexpr const char BRIGHTNESS[] = "brightness";
                           ^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:45:33: error: invalid case style for variable 'BRIGHTNESS' [readability-identifier-naming,-warnings-as-errors]
    static constexpr const char BRIGHTNESS[] = "brightness";
                                ^~~~~~~~~~
                                brightness
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:46:28: error: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays,-warnings-as-errors]
    static constexpr const char MAX_BRIGHTNESS[] = "max_brightness";
                           ^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:46:33: error: invalid case style for variable 'MAX_BRIGHTNESS' [readability-identifier-naming,-warnings-as-errors]
    static constexpr const char MAX_BRIGHTNESS[] = "max_brightness";
                                ^~~~~~~~~~~~~~
                                maxBrightness
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:47:28: error: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays,-warnings-as-errors]
    static constexpr const char TRIGGER[] = "trigger";
                           ^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:47:33: error: invalid case style for variable 'TRIGGER' [readability-identifier-naming,-warnings-as-errors]
    static constexpr const char TRIGGER[] = "trigger";
                                ^~~~~~~
                                trigger
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:48:28: error: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays,-warnings-as-errors]
    static constexpr const char DELAY_ON[] = "delay_on";
                           ^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:48:33: error: invalid case style for variable 'DELAY_ON' [readability-identifier-naming,-warnings-as-errors]
    static constexpr const char DELAY_ON[] = "delay_on";
                                ^~~~~~~~
                                delayOn
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:49:28: error: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays,-warnings-as-errors]
    static constexpr const char DELAY_OFF[] = "delay_off";
                           ^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:49:33: error: invalid case style for variable 'DELAY_OFF' [readability-identifier-naming,-warnings-as-errors]
    static constexpr const char DELAY_OFF[] = "delay_off";
                                ^~~~~~~~~
                                delayOff
../test/sysfs.cpp:62:46: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
        std::array<const char *, 4> attrs = {BRIGHTNESS, TRIGGER, DELAY_ON, DELAY_OFF};
                                             ^
../test/sysfs.cpp:62:58: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
        std::array<const char *, 4> attrs = {BRIGHTNESS, TRIGGER, DELAY_ON, DELAY_OFF};
                                                         ^
../test/sysfs.cpp:62:67: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
        std::array<const char *, 4> attrs = {BRIGHTNESS, TRIGGER, DELAY_ON, DELAY_OFF};
                                                                  ^
../test/sysfs.cpp:62:77: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
        std::array<const char *, 4> attrs = {BRIGHTNESS, TRIGGER, DELAY_ON, DELAY_OFF};
                                                                            ^
```

Change-Id: I1df5f9b9f6a8c2073a0bc04ea5f88c580e2cb1b9
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/sysfs.cpp b/sysfs.cpp
index 09bbc5d..277710d 100644
--- a/sysfs.cpp
+++ b/sysfs.cpp
@@ -54,47 +54,47 @@
 
 unsigned long SysfsLed::getBrightness()
 {
-    return getSysfsAttr<unsigned long>(root / BRIGHTNESS);
+    return getSysfsAttr<unsigned long>(root / attrBrightness);
 }
 
 void SysfsLed::setBrightness(unsigned long brightness)
 {
-    setSysfsAttr<unsigned long>(root / BRIGHTNESS, brightness);
+    setSysfsAttr<unsigned long>(root / attrBrightness, brightness);
 }
 
 unsigned long SysfsLed::getMaxBrightness()
 {
-    return getSysfsAttr<unsigned long>(root / MAX_BRIGHTNESS);
+    return getSysfsAttr<unsigned long>(root / attrMaxBrightness);
 }
 
 std::string SysfsLed::getTrigger()
 {
-    return getSysfsAttr<std::string>(root / TRIGGER);
+    return getSysfsAttr<std::string>(root / attrTrigger);
 }
 
 void SysfsLed::setTrigger(const std::string& trigger)
 {
-    setSysfsAttr<std::string>(root / TRIGGER, trigger);
+    setSysfsAttr<std::string>(root / attrTrigger, trigger);
 }
 
 unsigned long SysfsLed::getDelayOn()
 {
-    return getSysfsAttr<unsigned long>(root / DELAY_ON);
+    return getSysfsAttr<unsigned long>(root / attrDelayOn);
 }
 
 void SysfsLed::setDelayOn(unsigned long ms)
 {
-    setSysfsAttr<unsigned long>(root / DELAY_ON, ms);
+    setSysfsAttr<unsigned long>(root / attrDelayOn, ms);
 }
 
 unsigned long SysfsLed::getDelayOff()
 {
-    return getSysfsAttr<unsigned long>(root / DELAY_OFF);
+    return getSysfsAttr<unsigned long>(root / attrDelayOff);
 }
 
 void SysfsLed::setDelayOff(unsigned long ms)
 {
-    setSysfsAttr<unsigned long>(root / DELAY_OFF, ms);
+    setSysfsAttr<unsigned long>(root / attrDelayOff, ms);
 }
 } // namespace led
 } // namespace phosphor