igb: unused variable warning in igb remove

Wrap hw variable declaration in DCA flags to prevent unused variable
warning during compilation.
Signed-off-by: NAlexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>

drivers/net/igb/igb_main.c

@@ -1360,7 +1360,9 @@ static void __devexit igb_remove(struct pci_dev *pdev)
 {
 	struct net_device *netdev = pci_get_drvdata(pdev);
 	struct igb_adapter *adapter = netdev_priv(netdev);
+#ifdef CONFIG_DCA
 	struct e1000_hw *hw = &adapter->hw;
+#endif
 
 	/* flush_scheduled work may reschedule our watchdog task, so
 	 * explicitly disable watchdog tasks from being rescheduled  */