void ei_rx_overrun (struct net_device * dev);
we have to kick the 8390 to get it started again. Problem is that you have to kick it exactly as NS prescribes in the updated datasheets, or ``the NIC may act in an unpredictable manner.'' This includes causing ``the NIC to defer indefinitely when it is stopped on a busy network.'' Ugh. Called with lock held. Don't call this with the interrupts off or your computer will hate you - it takes 10ms or so.