sde: Add support for layer caching

1. Pass layer updating flag to composition manager to mark those
   layers for SDE composition.
2. Compare cached layer stack info with current layer stack info.
   if it matches then set composition type to HWC_OVERLAY, so that
   surfaceflinger wont compose those cached layers into framebuffer
3. Cache current layer stack information for next frame composition.

Change-Id: I3485a8ac2242fa25b48e79b1549d37ef7638c9af
5 files changed