tunnels: fix netns vs proto registration ordering

Same stuff as in ip_gre patch: receive hook can be called before netns
setup is done, oopsing in net_generic().

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static void x6spi_destroy_rcu(struct rcu_head *head)
{
	kmem_cache_free(xfrm6_tunnel_spi_kmem,
			container_of(head, struct xfrm6_tunnel_spi, rcu_head));
}

static void x6spi_destroy_rcu(struct rcu_head *head)
{
	kmem_cache_free(xfrm6_tunnel_spi_kmem,
			container_of(head, struct xfrm6_tunnel_spi, rcu_head));
}
