soc: mediatek: remove DDP_DOMPONENT_DITHER from enum

soc: mediatek: remove DDP_DOMPONENT_DITHER from enum

After mmsys and drm change DITHER enum to DDP_COMPONENT_DITHER0,
mmsys header can remove the useless DDP_COMPONENT_DITHER enum.

Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20230306080659.15261-3-jason-jh.lin@mediatek.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>