Add sunxi v4l2 rotation engine support to the drm_hwcomposer #66
Description
Sunxi display controlled has no support for rotated planes.
Instead it offers separate IP core to rotate buffer, which is exposed to user as v4l2 driver.
To off-load GPU with changed orientation, we can use that driver.
Case 1: No rotation
[hwc layer 1] -> [drm_plane 1]
[hwc layer 2] -> [drm_plane 2]
Case 2: Changed orientation
[hwc layer 1] -> [Rotate layer into new buffer, cache it] -> [drm_plane 1]
[hwc layer 2] -> [Rotate layer into new buffer, cache it] -> [drm_plane 2]