net: xscale: Fix return type for implementation of ndo_start_xmit

Since Linux now supports CFI, it will be a good idea to fix mismatched
return type for implementation of hooks. Otherwise this might get
cought out by CFI and cause a panic.

eth_xmit() would return either NETDEV_TX_BUSY or NETDEV_TX_OK, so
change the return type to netdev_tx_t directly.
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Link: https://lore.kernel.org/r/20220902081612.60405-1-guozihua@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/xscale/ixp4xx_eth.c

@@ -841,7 +841,7 @@ static void eth_txdone_irq(void *unused)
 	}
 }
 
-static int eth_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t eth_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct port *port = netdev_priv(dev);
 	unsigned int txreadyq = port->plat->txreadyq;