hwc: Implement mixed mode composition.

With this change we are moving  MDP composition from all-or-nothing
implementation to mixed mode implementation where layers can
partially be composited through MDP and while rest of the layers are
composed / cached in framebuffer.

        - Mixed mode design is based on layer caching
        - Mixed mode path is configured only when non-bypassing
          layers are cached.
        - Never allow mixed mode when FB needs to be  udpated.
        - If we cannot bypass all MDP comp marked layers, bail
          out completely.

Change-Id: Ie08f39db07e032b537f042d0d2bfe772ebfed049
11 files changed