lan78xx: throttle TX path at slower than SuperSpeed USB

Throttle TX path only at slower than SuperSpeed USB.
SuperSpeed USB has enough bandwidth to maintain GigE.

Signed-off-by: Woojung Huh <woojung.huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/lan78xx.c

@@ -2263,7 +2263,9 @@ netdev_tx_t lan78xx_start_xmit(struct sk_buff *skb, struct net_device *net)
 	if (skb2) {
 		skb_queue_tail(&dev->txq_pend, skb2);
 
-		if (skb_queue_len(&dev->txq_pend) > 10)
+		/* throttle TX patch at slower than SUPER SPEED USB */
+		if ((dev->udev->speed < USB_SPEED_SUPER) &&
+		    (skb_queue_len(&dev->txq_pend) > 10))
 			netif_stop_queue(net);
 	} else {
 		netif_dbg(dev, tx_err, dev->net,