ethernet: s2io: don't call dev_kfree_skb() under spin_lock_irqsave()

ethernet: s2io: don't call dev_kfree_skb() under spin_lock_irqsave()

It is not allowed to call kfree_skb() or consume_skb() from hardware
interrupt context or with hardware interrupts being disabled.

It should use dev_kfree_skb_irq() or dev_consume_skb_irq() instead.
The difference between them is free reason, dev_kfree_skb_irq() means
the SKB is dropped in error and dev_consume_skb_irq() means the SKB
is consumed in normal.

In this case, dev_kfree_skb() is called in free_tx_buffers() to drop
the SKBs in tx buffers, when the card is down, so replace it with
dev_kfree_skb_irq() here.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>