hwc: Add support for copybit(C2D) composition

- Add CopybitEngine to hwc_context
- draw the layer on the HWC_FRAMEBUFFER_TARGET using
  copybit(c2d) if it qualifies for C2D composition.
- use fence returned from the copybit during c2d
  composition

Change-Id: I052da015cd031f7abd6411d83d7944c335caeff7
11 files changed