Don't trust DozeState onScreenState changes

In DozeScreenBrightness, we should only rely on the passed
displayScreenState because our DozeState (updated by transitionTo)
may not be updated yet. Therefore, only register the brightness sensor
when the display state is Display.STATE_DOZE/DOZE_SUSPENDED.

Test: atest DozeScreenBrightnessTest
Bug: 168689990
Change-Id: Ie32f91c5a46bd987649a8a17e6543071847ad97c