netns: ip6mr: allocate mroute6_socket per-namespace.

Preliminary work to make IPv6 multicast forwarding netns-aware.

Make IPv6 multicast forwarding mroute6_socket per-namespace,
moves it into struct netns_ipv6.

At the moment, mroute6_socket is only referenced in init_net.

Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 2932721..8a0a67d 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -55,5 +55,8 @@
 	struct sock             *ndisc_sk;
 	struct sock             *tcp_sk;
 	struct sock             *igmp_sk;
+#ifdef CONFIG_IPV6_MROUTE
+	struct sock		*mroute6_sk;
+#endif
 };
 #endif