[media] ml86v7667: fix compiler warning

build/media_build/v4l/ml86v7667.c: In function 'ml86v7667_s_ctrl':
build/media_build/v4l/ml86v7667.c:120:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
  int ret = 0;
        ^

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Vladimir Barinov <source@cogentembedded.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/i2c/ml86v7667.c

@@ -117,7 +117,7 @@ static int ml86v7667_s_ctrl(struct v4l2_ctrl *ctrl)
 {
 	struct v4l2_subdev *sd = to_sd(ctrl);
 	struct i2c_client *client = v4l2_get_subdevdata(sd);
-	int ret = 0;
+	int ret;
 
 	switch (ctrl->id) {
 	case V4L2_CID_BRIGHTNESS: