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>

drivers/net/vxge/vxge-main.c

@@ -812,7 +812,7 @@ static int vxge_learn_mac(struct vxgedev *vdev, u8 *mac_header)
  * NOTE: when device cant queue the pkt, just the trans_start variable will
  * not be upadted.
 */
-static int
+static netdev_tx_t
 vxge_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct vxge_fifo *fifo = NULL;