Art confirms that this should work fine.  Since most panels are 18bpp
with dithering from 24bpp, the existing code wouldn't be enabled in most
cases.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>