drm/mediatek: Add mt8188 dsi compatible to mtk_dsi.c

Add the compatible because there are different definitions for cmdq
register bit control in mt8188.

Signed-off-by: Shuijing Li <shuijing.li@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20230911120800.17369-4-shuijing.li@mediatek.com/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>