healthd: fix include paths

This makes it possible to set the *_LED_PATH defines from the device's
BoardConfig.mk.

For some reason, these defines were set for healthd.cpp, not for
healthd_mode_charger.cpp, where they are actually used.

I think the issue was introduced with the merging of android-7.1.2_r2 in
commit e40b34d9.

Change-Id: I507f2cb4cb440f2a6584a59394a623e5ffa16864