qlcnic: Clear link status when interface is down

o When interface is down, mailbox command to get context statistics
  fails. So restrict driver from issuing get statistics command when
  interface is down.
Signed-off-by: NShahed Shaikh <shahed.shaikh@qlogic.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c

@@ -1412,6 +1412,7 @@ void __qlcnic_down(struct qlcnic_adapter *adapter, struct net_device *netdev)
 	smp_mb();
 	spin_lock(&adapter->tx_clean_lock);
 	netif_carrier_off(netdev);
+	adapter->ahw->linkup = 0;
 	netif_tx_disable(netdev);
 
 	qlcnic_free_mac_list(adapter);