mlx4_en: Fix not deleted napi structures

Napi structures are being created each time we open a port, but when
the port is closed the napi structure is only disabled but not removed.
This bug caused hang while removing the driver.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/mlx4/en_cq.c b/drivers/net/mlx4/en_cq.c
index 91f50de..a276125 100644
--- a/drivers/net/mlx4/en_cq.c
+++ b/drivers/net/mlx4/en_cq.c
@@ -125,8 +125,10 @@
 
 	if (cq->is_tx)
 		del_timer(&cq->timer);
-	else
+	else {
 		napi_disable(&cq->napi);
+		netif_napi_del(&cq->napi);
+	}
 
 	mlx4_cq_free(mdev->dev, &cq->mcq);
 }