bridge: notify mdb changes via netlink

As Stephen mentioned, we need to monitor the mdb
changes in user-space, so add notifications via netlink too.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index f95b766..2807c76 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -435,6 +435,8 @@
 extern int br_multicast_set_querier(struct net_bridge *br, unsigned long val);
 extern int br_multicast_set_hash_max(struct net_bridge *br, unsigned long val);
 extern void br_mdb_init(void);
+extern void br_mdb_notify(struct net_device *dev, struct net_bridge_port *port,
+			  struct br_ip *group, int type);
 
 static inline bool br_multicast_is_router(struct net_bridge *br)
 {