[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: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index e5ef597..09117d6 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -461,6 +461,7 @@
 			break;
 		}
 		read_unlock_bh(&idev->lock);
+		in6_dev_put(idev);
 	}
 	return im;
 }