hwc: Use basePipe for fullscreen and opaque layer

Usually 3 stages are available for MDP Composition.
One stage is reserved for FB. When bottomlayer is
fullscreen, we go for 4 MDP stages by configuring
the borderfill pipe. Bottom layer should be opaque
without any blending required.

Change-Id: I6ec1067040802d564f989775610355159607cc40
1 file changed