media: v4l2-ctrls.c: initialize an error return code with zero

Fix this smatch error:

drivers/media/v4l2-core/v4l2-ctrls.c:2971 v4l2_ctrl_request_clone() error: uninitialized symbol 'err'.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/v4l2-core/v4l2-ctrls.c

@@ -2879,7 +2879,7 @@ static int v4l2_ctrl_request_clone(struct v4l2_ctrl_handler *hdl,
 				   const struct v4l2_ctrl_handler *from)
 {
 	struct v4l2_ctrl_ref *ref;
-	int err;
+	int err = 0;
 
 	if (WARN_ON(!hdl || hdl == from))
 		return -EINVAL;