IB/ipoib: For sendonly join free the multicast group on leave

When we leave the multicast group on expiration of a neighbor we
do not free the mcast structure. This results in a memory leak
that causes ib_dealloc_pd to fail and print a WARN_ON message
and backtrace.

Fixes: bd99b2e05c (IB/ipoib: Expire sendonly multicast joins)
Signed-off-by: Christoph Lameter <cl@linux.com>
Tested-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -1207,8 +1207,10 @@ static void __ipoib_reap_neigh(struct ipoib_dev_priv *priv)
 
 out_unlock:
 	spin_unlock_irqrestore(&priv->lock, flags);
-	list_for_each_entry_safe(mcast, tmcast, &remove_list, list)
+	list_for_each_entry_safe(mcast, tmcast, &remove_list, list) {
 		ipoib_mcast_leave(dev, mcast);
+		ipoib_mcast_free(mcast);
+	}
 }
 
 static void ipoib_reap_neigh(struct work_struct *work)