drm_hwcomposer: Don't composite over protected layers

This patch changes two things with respect to protected layers:

1- It provisions the HW plane in the correct position. ie: if
   the background layer is slated for a HW plane, it will be
   placed on the primary layer and the protected layer will be
   placed on top of it.
2- It punches a hole through the precomposite and squash layers
   such that when they are placed on top of the protected layer,
   they do not obstruct it.

TEST=Tested on smaug with multi-window with a variety of different
     layouts and visible layers

Change-Id: Ie30939f2bb750dbe3faa558ddb094b677f41f45e
Signed-off-by: Sean Paul <seanpaul@chromium.org>
2 files changed