[IPV6] don't try to insert same local route multiple times.

Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>

net/ipv6/addrconf.c

@@ -1457,8 +1457,7 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len)
 				spin_unlock(&ifp->lock);
 
 				if (!(flags&IFA_F_TENTATIVE))
-					ipv6_ifa_notify((flags&IFA_F_DEPRECATED) ?
-							0 : RTM_NEWADDR, ifp);
+					ipv6_ifa_notify(0, ifp);
 			} else
 				spin_unlock(&ifp->lock);