net: cpmac: 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/ti/cpmac.c

@@ -532,7 +532,7 @@ static int cpmac_poll(struct napi_struct *napi, int budget)
 
 }
 
-static int cpmac_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t cpmac_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	int queue;
 	unsigned int len;