[media] uvc: fix sparse warning

drivers/media/usb/uvc/uvc_video.c:1466:38: warning: incorrect type in return expression (different base types)

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>