drm/mediatek: dpi: Remove output format of YUV

DPI is not support output format as YUV, but there is the setting of
configuring output YUV. Therefore, remove them in this patch.

Fixes: 9e629c17 ("drm/mediatek: Add DPI sub driver")
Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20220701035845.16458-5-rex-bc.chen@mediatek.com/


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