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/dl2k.c b/drivers/net/dl2k.c
index 4b6a219..7fa7a90 100644
--- a/drivers/net/dl2k.c
+++ b/drivers/net/dl2k.c
@@ -59,7 +59,7 @@
 static void rio_timer (unsigned long data);
 static void rio_tx_timeout (struct net_device *dev);
 static void alloc_list (struct net_device *dev);
-static int start_xmit (struct sk_buff *skb, struct net_device *dev);
+static netdev_tx_t start_xmit (struct sk_buff *skb, struct net_device *dev);
 static irqreturn_t rio_interrupt (int irq, void *dev_instance);
 static void rio_free_tx (struct net_device *dev, int irq);
 static void tx_error (struct net_device *dev, int tx_status);
@@ -600,7 +600,7 @@
 	return;
 }
 
-static int
+static netdev_tx_t
 start_xmit (struct sk_buff *skb, struct net_device *dev)
 {
 	struct netdev_private *np = netdev_priv(dev);