Fix this smatch error:

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