A machine may need to invert the panel backlight brightness value. This
patch adds the infrastructure for a quirk to do so.
Signed-off-by: NCarsten Emde <C.Emde@osadl.org>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>