hwc: update swapchain to save/restore plane position & size

hwc: update swapchain to save/restore plane position & size

BZ: 28857

Kernel patch for sprite + overlay blending support.

This patch sets primary plane pixel format to BRGA8888 to support
premultipled alpha blending between sprite & overlay planes.

Change-Id: I9d7252e5bf45c95015eff73dbde04df8212f7e61
Signed-off-by: Jackie Li <yaodong.li@intel.com>
Reviewed-on: http://android.intel.com:8080/41994
Reviewed-by: Hu, Austin <austin.hu@intel.com>
Reviewed-by: Xu, Randy <randy.xu@intel.com>
Tested-by: Tong, BoX <box.tong@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>