drm/i915/skl: Add 180 degree HW rotation support

Add support for 180 degree rotation for primary and sprite planes

Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>