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/8390.c

@@ -17,7 +17,7 @@ int ei_close(struct net_device *dev)
 }
 EXPORT_SYMBOL(ei_close);
 
-int ei_start_xmit(struct sk_buff *skb, struct net_device *dev)
+netdev_tx_t ei_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	return __ei_start_xmit(skb, dev);
 }