media: uvcvideo: Fix smatch warning

drivers/media/usb/uvc/uvc_video.c: drivers/media/usb/uvc/uvc_video.c:1893 uvc_video_start_transfer() warn: argument 2 to %u specifier is cast from pointer

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>