removed useless check for button backlight value

Change-Id: I4013061f7c2d7c2955076c8a5d9bb6ace0b081bc

Conflicts:
	services/java/com/android/server/power/DisplayPowerController.java
update button light on/off correctly on change

Change-Id: I597d647a168015d553e1ce8acd46f1d98d12dd34