Listen for screen power changes in ClockEventController

To reduce impact this only refreshes the clock, instead of all elements
of the AOD display. The remaining elements may not update until the
minute rolls over.

Bug: 390191659
Test: Manually reproduced issue
Flag: NONE Targetted minimal bug fix
Change-Id: I3a3329d9b9a29f5452572ec23812b3e4edd2a378