igc: Fix igc_uc_unsync()

In case igc_del_mac_filter() returns error, that error is masked
since the functions always return 0 (success). This patch fixes
igc_uc_unsync() so it returns whatever value igc_del_mac_filter()
returns (0 on success, negative number on error).
Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igc/igc_main.c

@@ -2284,9 +2284,7 @@ static int igc_uc_unsync(struct net_device *netdev, const unsigned char *addr)
 {
 	struct igc_adapter *adapter = netdev_priv(netdev);
 
-	igc_del_mac_filter(adapter, addr, adapter->num_rx_queues, 0);
-
-	return 0;
+	return igc_del_mac_filter(adapter, addr, adapter->num_rx_queues, 0);
 }
 
 /**