net: sunplus: 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.

spl2sw_ethernet_start_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/20220902081550.60095-1-guozihua@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sunplus/spl2sw_driver.c

@@ -62,7 +62,8 @@ static int spl2sw_ethernet_stop(struct net_device *ndev)
 	return 0;
 }
 
-static int spl2sw_ethernet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
+static netdev_tx_t spl2sw_ethernet_start_xmit(struct sk_buff *skb,
+					      struct net_device *ndev)
 {
 	struct spl2sw_mac *mac = netdev_priv(ndev);
 	struct spl2sw_common *comm = mac->comm;