Merge branch 'udp_tunnel'

Tom Herbert says:

====================
udp: UDP tunnel enhancements

- Add udp_sock_create in new helper module udp_tunnel. Tunnel
  implementations call this function to create listener UDP ports.
- Make vxlan and l2tp call udp_sock_create.
- Move udp_tunnel_segment into udp_offload.c.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>