[code] new NAPI helper functions

[Jeff Garzik <jgarzik@pobox.com>]

Here are some functions in tg3, that I would like to eventually make 
available to all net drivers (and other net stack users).
/* these three netif_xxx funcs should be moved into generic net layer */
static void netif_poll_disable(struct net_device *dev)
{
	while (test_and_set_bit(__LINK_STATE_RX_SCHED, &dev->state)) {
		current->state = TASK_INTERRUPTIBLE;
		schedule_timeout(1);
	}
}

static inline void netif_poll_enable(struct net_device *dev)
{
	clear_bit(__LINK_STATE_RX_SCHED, &dev->state);
}

/* same as netif_rx_complete, except that local_irq_save(flags)
 * has already been issued
 */
static inline void __netif_rx_complete(struct net_device *dev)
{
	if (!test_bit(__LINK_STATE_RX_SCHED, &dev->state)) BUG();
	list_del(&dev->poll_list);
	clear_bit(__LINK_STATE_RX_SCHED, &dev->state);
}