[media] ml86v7667: fix compile warning: 'ret' set but not used

media_build/v4l/ml86v7667.c: In function 'ml86v7667_s_ctrl':
media_build/v4l/ml86v7667.c:120:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
int ret;
^
And indeed, ret is set but not used. Let's actually return the error
code.

Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/i2c/ml86v7667.c

···
 {
 	struct v4l2_subdev *sd = to_sd(ctrl);
 	struct i2c_client *client = v4l2_get_subdevdata(sd);
-	int ret;
+	int ret = -EINVAL;
 
 	switch (ctrl->id) {
 	case V4L2_CID_BRIGHTNESS:
···
 		break;
 	}
 
-	return 0;
+	return ret;
 }
 
 static int ml86v7667_querystd(struct v4l2_subdev *sd, v4l2_std_id *std)