media: mediatek: vcodec: Fix v4l2 compliance decoder cmd test fail

Will return -EINVAL using standard framework api when test stateless
decoder with cmd VIDIOC_(TRY)DECODER_CMD. Disable them to adjust v4l2
compliance test for user driver(GStreamer/Chrome) won't use decoder cmd.

Fixes: 8cdc3794

 ("media: mtk-vcodec: vdec: support stateless API")
Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>