tun: Fix copy/paste error in tun_get_user

Use the right structure while incrementing the offset in tun_get_user.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed