healthd: Add callback for screen_on to the healthdHAL

Adds a callback to the healthdHAL which can check for device specific
properties to decide if the screen should turn on.

Change-Id: I543e7729ecb291157df4d3be1bd718f8af01ac40
Signed-off-by: Ruchi <Kandoi&lt;kandoiruchi@google.com>