hns: remove useless void cast

There is no need to cast away return value of dev_close.
Signed-off-by: NStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns/hns_ethtool.c

@@ -595,7 +595,7 @@ static void hns_nic_self_test(struct net_device *ndev,
 		set_bit(NIC_STATE_TESTING, &priv->state);
 
 		if (if_running)
-			(void)dev_close(ndev);
+			dev_close(ndev);
 
 		for (i = 0; i < SELF_TEST_TPYE_NUM; i++) {
 			if (!st_param[i][1])