[PATCH] IPoIB: Fix device removal race

Currently we may have work scheduled in default kernel workqueue when
the device is going down.  The device could get freed before this
workqueue gets serviced.  I am actually seeing this causing system
hangs.

The following patch fixes this by using ipoib_workqueue which gets
flushed when the device is going down.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -672,7 +672,7 @@ static void ipoib_set_mcast_list(struct net_device *dev)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 
-	schedule_work(&priv->restart_task);
+	queue_work(ipoib_workqueue, &priv->restart_task);
 }
 
 static void ipoib_neigh_destructor(struct neighbour *n)