arm64: dts: mediatek: mt8173: Add gce-client-reg handle to disp-mutex

Add a gce client reg handle to the disp mutex to enable MT8173
platforms to use MediaTek's CMDQ for extra performance.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220228110329.245366-1-angelogioacchino.delregno@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>