tools: Fix some warnings by cppcheck

Warning message:
tools/i2c/i2c.hpp:30:9: performance: Variable 'busStr' is assigned in
constructor body. Consider performing initialization in
initialization list. [useInitializationList]
        busStr = "/dev/i2c-" + std::to_string(busId);
        ^

tools/power-utils/updater.cpp:213:18: style: Local variable 'devPath'
shadows outer variable [shadowVariable]
            auto devPath = internal::getDevicePath(p);
                 ^
tools/power-utils/updater.hpp:108:17: note: Shadowed declaration
    std::string devPath;
                ^
tools/power-utils/updater.cpp:213:18: note: Shadow variable
            auto devPath = internal::getDevicePath(p);
                 ^

Tested: Verify that there are no such warnings in local CI.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Ibc7536345ee40579256c398646ad00a05b686ab3
diff --git a/tools/i2c/i2c.hpp b/tools/i2c/i2c.hpp
index 23acdbc..5a01ebf 100644
--- a/tools/i2c/i2c.hpp
+++ b/tools/i2c/i2c.hpp
@@ -25,9 +25,9 @@
                        InitialState initialState = InitialState::OPEN,
                        int maxRetries = 0) :
         busId(busId),
-        devAddr(devAddr), maxRetries(maxRetries)
+        devAddr(devAddr), maxRetries(maxRetries),
+        busStr("/dev/i2c-" + std::to_string(busId))
     {
-        busStr = "/dev/i2c-" + std::to_string(busId);
         if (initialState == InitialState::OPEN)
         {
             open();