[IPV6]: /proc/net/anycast6 unbalanced inet6_dev refcnt

Reading /proc/net/anycast6 when there is no anycast address
on an interface results in an ever-increasing inet6_dev reference
count, as well as a reference to the netdevice you can't get rid of.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/anycast.c

@@ -461,6 +461,7 @@ static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
 			break;
 		}
 		read_unlock_bh(&idev->lock);
+		in6_dev_put(idev);
 	}
 	return im;
 }