media: mtk-vcodec: vdec: use helpers in VIDIOC_(TRY_)DECODER_CMD

Let's use the dedicated helpers to make sure we get the expected
behavior and remove redundant code.
Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c

@@ -484,18 +484,7 @@ static void mtk_vdec_worker(struct work_struct *work)
 static int vidioc_try_decoder_cmd(struct file *file, void *priv,
 				struct v4l2_decoder_cmd *cmd)
 {
-	switch (cmd->cmd) {
-	case V4L2_DEC_CMD_STOP:
-	case V4L2_DEC_CMD_START:
-		if (cmd->flags != 0) {
-			mtk_v4l2_err("cmd->flags=%u", cmd->flags);
-			return -EINVAL;
-		}
-		break;
-	default:
-		return -EINVAL;
-	}
-	return 0;
+	return v4l2_m2m_ioctl_try_decoder_cmd(file, priv, cmd);
 }