hwcomposer: 7x30: disable overlays for video playback

check MDP revision and disable overlays for video playback usecase
on 7x30.

Ported from jellybean (was Change-Id: I8b179512b4aff136834dd80e4da7227a6b2aff4e)

http://review.cyanogenmod.com/24765

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: Iec842ee828483d952a245ba482f0b780da2708ef