hwc: Drop alpha from writeback

The alpha in the writeback is unused right now. Force MDP to use
RGBX for composing writeback.
Bug: 11479817

Change-Id: I87e3fff962283af05a07d28698811a4402f2606c
1 file changed
tree: 738f7ab9c101feb8040471effe0b5f67b4adbdac
  1. Android.mk
  2. msm8960/
  3. msm8974/
  4. msm8x26/