power: Simplify display_hint_sent

Check for whether the display hint has been sent at the start
of the set_interactive() function in the common powerHAL.

This gets rid of the need to replicate the same variable in
every target-specific powerHAL that implements the
set_interactive_override() function.

Change-Id: If7dd11fcb578211f4f83847f9257232c4138ce53
4 files changed