igb: set num_rx/tx_queues to 0 when queues are freed

An issue was seen on suspend in which the system reported a page fault.  This
was due to the new reg_idx code being called after the queues were freed.

This update prevents any for loops from going through the queues by setting
the number of queues to 0 when they are freed.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -420,6 +420,9 @@ static void igb_free_queues(struct igb_adapter *adapter)
 	for (i = 0; i < adapter->num_rx_queues; i++)
 		netif_napi_del(&adapter->rx_ring[i].napi);
 
+	adapter->num_rx_queues = 0;
+	adapter->num_tx_queues = 0;
+
 	kfree(adapter->tx_ring);
 	kfree(adapter->rx_ring);
 }