net: pch_gbe: remove unneeded variable retval in __pch_gbe_suspend

Fix the following coccicheck warning:

./drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c:2415:5-11: Unneeded variable: "retval". Return "0" on line 2435
Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Link: https://lore.kernel.org/r/1604837580-12419-1-git-send-email-kaixuxia@tencent.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c

@@ -2412,7 +2412,6 @@ static int __pch_gbe_suspend(struct pci_dev *pdev)
 	struct pch_gbe_adapter *adapter = netdev_priv(netdev);
 	struct pch_gbe_hw *hw = &adapter->hw;
 	u32 wufc = adapter->wake_up_evt;
-	int retval = 0;
 
 	netif_device_detach(netdev);
 	if (netif_running(netdev))
@@ -2432,7 +2431,7 @@ static int __pch_gbe_suspend(struct pci_dev *pdev)
 		pch_gbe_mac_set_wol_event(hw, wufc);
 		pci_disable_device(pdev);
 	}
-	return retval;
+	return 0;
 }
 
 #ifdef CONFIG_PM