net: hns3: fix return type of ndo_start_xmit function

The method ndo_start_xmit() is defined as returning an 'netdev_tx_t',
which is a typedef for an enum type, also the implementation in this
driver has returns 'netdev_tx_t' value, so just change the function
return type to netdev_tx_t.

Found by coccinelle.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hix5hd2_gmac.c

@@ -736,7 +736,7 @@ static int hix5hd2_fill_sg_desc(struct hix5hd2_priv *priv,
 	return 0;
 }
 
-static int hix5hd2_net_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t hix5hd2_net_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct hix5hd2_priv *priv = netdev_priv(dev);
 	struct hix5hd2_desc *desc;