drm/mediatek: Fix underrun in VDO1 when switches off the layer

Do not reset Merge while using CMDQ because reset API doesn't
wait for frame done event as CMDQ does and could lead to
underrun when the layer is switching off.

Fixes: aaf94f7c ("drm/mediatek: Add display merge async reset control")

Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20231214055847.4936-23-shawn.sung@mediatek.com/


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