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/starfire.c b/drivers/net/starfire.c
index 5e7645e..a36e2b5 100644
--- a/drivers/net/starfire.c
+++ b/drivers/net/starfire.c
@@ -595,7 +595,7 @@
 static void	check_duplex(struct net_device *dev);
 static void	tx_timeout(struct net_device *dev);
 static void	init_ring(struct net_device *dev);
-static int	start_tx(struct sk_buff *skb, struct net_device *dev);
+static netdev_tx_t start_tx(struct sk_buff *skb, struct net_device *dev);
 static irqreturn_t intr_handler(int irq, void *dev_instance);
 static void	netdev_error(struct net_device *dev, int intr_status);
 static int	__netdev_rx(struct net_device *dev, int *quota);
@@ -1223,7 +1223,7 @@
 }
 
 
-static int start_tx(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t start_tx(struct sk_buff *skb, struct net_device *dev)
 {
 	struct netdev_private *np = netdev_priv(dev);
 	unsigned int entry;