Merge branch 'gtp-simple-improvements'

Andreas Schultz says:

====================
gtp: simple gtp improvements

This is the part of the previous "simple gtp improvements" series
that Pablo indicated should go into net-next.

The rcu_lock removal is small correctness changes. Passing invalid
to user space allows for more standards compliant handling of invalid
tunnels.
====================

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