netns: ip6mr: declare reg_vif_num per-namespace

Preliminary work to make IPv6 multicast forwarding netns-aware.

Declare variable 'reg_vif_num' per-namespace, moves into struct netns_ipv6.

At the moment, this variable 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 919cb0f..afab4e4 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -63,6 +63,9 @@
 	atomic_t		cache_resolve_queue_len;
 	int			mroute_do_assert;
 	int			mroute_do_pim;
+#ifdef CONFIG_IPV6_PIMSM_V2
+	int			mroute_reg_vif_num;
+#endif
 #endif
 };
 #endif