sysfs: Fix readability-inconsistent-declaration-parameter-name

```
../sysfs.hpp:35:18: error: function 'phosphor::led::SysfsLed::setBrightness' has a definition with different parameter names [readability-inconsistent-declaration-parameter-name,-warnings-as-errors]
    virtual void setBrightness(unsigned long value);
                 ^
../sysfs.cpp:60:16: note: the definition seen here
void SysfsLed::setBrightness(unsigned long brightness)
               ^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../sysfs.hpp:35:18: note: differing parameters are named here: ('value'), in definition: ('brightness')
    virtual void setBrightness(unsigned long value);
                 ^                           ~~~~~
                                             brightness
```

Change-Id: Ib94099e118839d5d55071984d0cb4156c4d4f506
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/sysfs.hpp b/sysfs.hpp
index 752bc57..b65deff 100644
--- a/sysfs.hpp
+++ b/sysfs.hpp
@@ -32,7 +32,7 @@
     virtual ~SysfsLed() = default;
 
     virtual unsigned long getBrightness();
-    virtual void setBrightness(unsigned long value);
+    virtual void setBrightness(unsigned long brightness);
     virtual unsigned long getMaxBrightness();
     virtual std::string getTrigger();
     virtual void setTrigger(const std::string& trigger);