r8169: use dev_kfree_skb() instead of dev_kfree_skb_irq()

rtl8169_tx_interrupt() is used from NAPI context, it can
directly free skbs. dev_kfree_skb_irq() is a leftover from
pre-NAPI times of this driver.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/r8169.c

@@ -3379,7 +3379,7 @@ static void rtl8169_tx_interrupt(struct net_device *dev,
 		rtl8169_unmap_tx_skb(tp->pci_dev, tx_skb, tp->TxDescArray + entry);
 
 		if (status & LastFrag) {
-			dev_kfree_skb_irq(tx_skb->skb);
+			dev_kfree_skb(tx_skb->skb);
 			tx_skb->skb = NULL;
 		}
 		dirty_tx++;