soc: mediatek: mtk-mmsys: Add .remove() callback

Add a .remove() callback to correctly unregister the multimedia clocks
and DRM drivers.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230222094253.23678-2-angelogioacchino.delregno@collabora.com


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