drm: Add DRM_ROTATE_MASK and DRM_REFLECT_MASK

Makes it cleaner to separate the two from rotation variable.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>