There is no point in flipping a buffer for a disabled crtc.
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>