net: dscc4: replace dev_kfree_skb_irq by dev_consume_skb_irq for drop profiles

dev_consume_skb_irq() should be called in dscc4_tx_irq() when skb
xmit done. It makes drop profiles(dropwatch, perf) more friendly.

Signed-off-by: Yang Wei <yang.wei9@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/dscc4.c

@@ -1575,7 +1575,7 @@ try:
 					dev->stats.tx_packets++;
 					dev->stats.tx_bytes += skb->len;
 				}
-				dev_kfree_skb_irq(skb);
+				dev_consume_skb_irq(skb);
 				dpriv->tx_skbuff[cur] = NULL;
 				++dpriv->tx_dirty;
 			} else {