[media] uvcvideo: Return -ENOTTY in case of unknown ioctl

-EINVAL is the wrong error code in that case, replace it with -ENOTTY.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>