Add mmsys driver data and compatible for MT8186 in mtk_drm_drv.c.

Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20220421051218.8652-2-rex-bc.chen@mediatek.com/Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>