Customer report of a panic on boot due to the old

"m_getjcl:invalid cluster type" that occurred some
time back with the igb driver. This happens often when
booting over the net. I believe the NIC hardware is left
in a warm state when handed over to the driver, and a stray
RX interrupt happens earlier than the code is prepared for
it to happen. This change was verified to fix the problem,
its kind of a bandaid... but it is similar to what was done
in the igb code.

sys/dev/e1000/if_em.c

@@ -1570,6 +1570,8 @@ em_msix_rx(void *arg)
 	bool		more;
 
 	++rxr->rx_irq;
+	if (!(adapter->ifp->if_drv_flags & IFF_DRV_RUNNING))
+		return;
 	more = em_rxeof(rxr, adapter->rx_process_limit, NULL);
 	if (more)
 		taskqueue_enqueue(rxr->tq, &rxr->rx_task);