net: hns3: fix for changing MTU

when changing MTU, The new MTU must need to be set to netdevice.

Fixes: a8e8b7ff ("net: hns3: Add support to change MTU in HNS3 hardware")
Signed-off-by: NFuyun Liang <liangfuyun1@huawei.com>
Signed-off-by: NPeng Li <lipeng321@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3_enet.c

@@ -1413,6 +1413,8 @@ static int hns3_nic_change_mtu(struct net_device *netdev, int new_mtu)
 		return ret;
 	}
 
+	netdev->mtu = new_mtu;
+
 	/* if the netdev was running earlier, bring it up again */
 	if (if_running && hns3_nic_net_open(netdev))
 		ret = -EINVAL;