[IPV6]: Call inet6addr_chain notifiers on link down

Currently if the link is brought down via ip link or ifconfig down,
the inet6addr_chain notifiers are not called even though all
the addresses are removed from the interface.  This caused SCTP
to add duplicate addresses to it's list.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -2475,6 +2475,7 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 		write_unlock_bh(&idev->lock);
 
 		__ipv6_ifa_notify(RTM_DELADDR, ifa);
+		atomic_notifier_call_chain(&inet6addr_chain, NETDEV_DOWN, ifa);
 		in6_ifa_put(ifa);
 
 		write_lock_bh(&idev->lock);