bonding: rejoin multicast groups on VLANs

During a failover, the IGMP membership is sent to update
the switch restoring the traffic, but it misses groups added
to VLAN devices running on top of bonding devices.

This patch changes it to iterate over all VLAN devices
on top of it sending IGMP memberships too.

Signed-off-by: Flavio Leitner <fleitner@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index c6fdd85..308ed10 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -223,6 +223,7 @@
 	struct   delayed_work arp_work;
 	struct   delayed_work alb_work;
 	struct   delayed_work ad_work;
+	struct   delayed_work mcast_work;
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 	struct   in6_addr master_ipv6;
 #endif