drm/mediatek: Set dpi format in mmsys

Dpi output needs to adjust the output format to dual edge for MT8186.

Co-developed-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: Xinlei Lee <xinlei.lee@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/1666577099-3859-3-git-send-email-xinlei.lee@mediatek.com/


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