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/lib8390.c b/drivers/net/lib8390.c
index d6be360..2561198 100644
--- a/drivers/net/lib8390.c
+++ b/drivers/net/lib8390.c
@@ -299,7 +299,8 @@
  * Sends a packet to an 8390 network device.
  */
 
-static int __ei_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t __ei_start_xmit(struct sk_buff *skb,
+				   struct net_device *dev)
 {
 	unsigned long e8390_base = dev->base_addr;
 	struct ei_device *ei_local = (struct ei_device *) netdev_priv(dev);