hwc : Add hw limitation checks for MDP compposition.

Add hw limitation checks for MDP composition once
we identify actual layers for MDP. This should be generic
way for all basic hw limitations of underlying MDP/MDSS.
Current limitations:
- a-family : MDP can not handle alpha scaling.
- 8226 & 8974 : Can not handle if multiple layers need
  downscaling and blending

Change-Id: Ia944802d798f2d0e9cd4515d7e9854c7314cac78
CRs-fixed: 538803
4 files changed