bridge: implement multicast fast leave

V3: make it a flag
V2: make the toggle per-port

Fast leave allows bridge to immediately stops the multicast
traffic on the port receives IGMP Leave when IGMP snooping is enabled,
no timeouts are observed.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index cdbf904..cd86222 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -137,11 +137,11 @@
 #define BR_HAIRPIN_MODE		0x00000001
 #define BR_BPDU_GUARD           0x00000002
 #define BR_ROOT_BLOCK		0x00000004
+#define BR_MULTICAST_FAST_LEAVE	0x00000008
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 	u32				multicast_startup_queries_sent;
 	unsigned char			multicast_router;
-	unsigned char			multicast_fast_leave;
 	struct timer_list		multicast_router_timer;
 	struct timer_list		multicast_query_timer;
 	struct hlist_head		mglist;