drm/mediatek: Add MT8186 DSI compatible for mtk_drm_drv.c

The compatible "mediatek,mt8186-dsi" is used by MT8186 DSI, so
add it to mtk_ddp_comp_dt_ids in mtk_drm_drv.c.

Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20220504091923.2219-5-rex-bc.chen@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>