This patch makes the netif_rx_complete() and rx_interrupt_enable
  atomic when exiting the poll() method, so to avoid interrupt in poll.
  It also fixes the rx interrupt check logic in interrupt handler.
Signed-off-by: NLiu Tao <liutao1980@gmail.com>
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>