Merge branch 'udp-tunnel-common'

Andy Zhou says:

====================
Refactor vxlan and l2tp to use new common UDP tunnel APIs

This patch series add a few more UDP tunnel APIs and refactoring current
UDP tunnel based protocols, vxlan and l2tp to make use of the new APIs.

The added APIs are setup_udp_tunnel_sock(), udp_tunnel_xmit_skb() and
udp_tunnel_sock_release(). Those implementation logics already exist in
current vxlan and l2tp implementation. Move them to common APIs to reduce
code duplications.

Also split udp_tunnel.c into net/ipv4/udp_tunnel.c and
net/ipv6/ip6_udp_tunnel.c to maintain proper IP protocol separation.
====================

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