ipv6: struct xfrm6_tunnel in read_mostly section

tunnel6_handlers chain being scanned for each incoming packet,
make sure it doesnt share an often dirtied cache line.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc net/ipv6/ip6_tunnel.c
Simple merge

diff --cc net/ipv6/tunnel6.c
Simple merge

diff --cc net/ipv6/xfrm6_tunnel.c
Simple merge