net: cortina: Fix use correct return type for ndo_start_xmit()

The method ndo_start_xmit() returns a value of type netdev_tx_t. Fix
the ndo function to use the correct type.
Signed-off-by: NYunjian Wang <wangyunjian@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/cortina/gemini.c

@@ -1224,7 +1224,8 @@ static int gmac_map_tx_bufs(struct net_device *netdev, struct sk_buff *skb,
 	return -ENOMEM;
 }
 
-static int gmac_start_xmit(struct sk_buff *skb, struct net_device *netdev)
+static netdev_tx_t gmac_start_xmit(struct sk_buff *skb,
+				   struct net_device *netdev)
 {
 	struct gemini_ethernet_port *port = netdev_priv(netdev);
 	unsigned short m = (1 << port->txq_order) - 1;