netdev: convert bulk of drivers to netdev_tx_t

In a couple of cases collapse some extra code like:
   int retval = NETDEV_TX_OK;
   ...
   return retval;
into
   return NETDEV_TX_OK;

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ks8851.c b/drivers/net/ks8851.c
index 9a1dea6..547ac7c 100644
--- a/drivers/net/ks8851.c
+++ b/drivers/net/ks8851.c
@@ -868,11 +868,12 @@
  * and secondly so we can round up more than one packet to transmit which
  * means we can try and avoid generating too many transmit done interrupts.
  */
-static int ks8851_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t ks8851_start_xmit(struct sk_buff *skb,
+				     struct net_device *dev)
 {
 	struct ks8851_net *ks = netdev_priv(dev);
 	unsigned needed = calc_txlen(skb->len);
-	int ret = NETDEV_TX_OK;
+	netdev_tx_t ret = NETDEV_TX_OK;
 
 	if (netif_msg_tx_queued(ks))
 		ks_dbg(ks, "%s: skb %p, %d@%p\n", __func__,