liboverlay: Rotator-assisted MDP downscaling of videos.

Engage the rotator to assist MDP in performing video downscale for
primary and external. This saves bandwidth and avoids causing the
driver to make too many panel mode switches between BLT (writeback)
and non-BLT (direct) modes.

Change-Id: Icfabc2c0f978a23cf96c78a9976cf69cea697b5f
CRs-Fixed: 434852
14 files changed