Our display engine endpoints trigger some DTC warnings due to the fact that
we're having a single endpoint that doesn't need any reg property, and
since we don't have a reg property, we don't need the address-cells and
size-cells properties anymore.

Fix those
Acked-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@bootlin.com>