lan78xx: Fix failure in USB Full Speed

Fix initialize the uninitialized tx_qlen to an appropriate value when USB
Full Speed is used.

Fixes: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Yuiko Oshino <yuiko.oshino@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/lan78xx.c

@@ -2396,6 +2396,7 @@ static int lan78xx_reset(struct lan78xx_net *dev)
 		buf = DEFAULT_BURST_CAP_SIZE / FS_USB_PKT_SIZE;
 		dev->rx_urb_size = DEFAULT_BURST_CAP_SIZE;
 		dev->rx_qlen = 4;
+		dev->tx_qlen = 4;
 	}
 
 	ret = lan78xx_write_reg(dev, BURST_CAP, buf);