blank_screen: shut off all lights

This is used to make the phone appear off by init
during late boot (e.x. fsck for disk health), so
it should shut off all lights (not just the screen).

Bug: 74976325
Test: blank_screen
Change-Id: I790cc3dd856c2c2095fa3cf82519fd30834304ca
Merged-In: I790cc3dd856c2c2095fa3cf82519fd30834304ca