SurfaceFlinger: Add support for MDP3

SurfaceFlinger: Add support for MDP3

This change is porting of following commits related to MDP3

1) SurfaceFlinger: Change to support framebuffer flip for 2D blitters
- Surfaceflinger does not flip framebuffers when there are
  no layers marked for HWC_FRAMEBUFFER
- This change checks for the HWC_BLIT flag and will request a flip
  to a new FB_TARGET buffer even if there are no FRAMEBUFFER layers

  "Change-Id: I1cb44389a05c9ec049d7f0d39c288feccb11a91c"

2) SF: Avoid wormhole clear for BLIT calls
- Do not call GPU clear from SF when composition
  type is BLIT as it'll be taken care in HAL.

  "Change-Id: Ia613eb9b824c6484ecc8c8fa4ee883545d8541b8"

3) surfaceflinger: Allow gpu to render widevine level3
- Allow gpu to render widevine level3 but keep
  blocking screen shots.

  "Change-Id: I914232a062acbb7b17901dbf2b414973230e59d9"

Change-Id: I35eef9eb1597af21c195e07d5fe4c0c73ab3a269