net:dl2k: Replace dev_kfree_skb_irq by dev_consume_skb_irq

dev_consume_skb_irq() should be called when skb xmit
done.It makes drop profiles more friendly.

Signed-off-by: Huang Zijiang <huang.zijiang@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>