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/epic100.c b/drivers/net/epic100.c
index d668ff2..641a10d 100644
--- a/drivers/net/epic100.c
+++ b/drivers/net/epic100.c
@@ -298,7 +298,8 @@
 static void epic_timer(unsigned long data);
 static void epic_tx_timeout(struct net_device *dev);
 static void epic_init_ring(struct net_device *dev);
-static int epic_start_xmit(struct sk_buff *skb, struct net_device *dev);
+static netdev_tx_t epic_start_xmit(struct sk_buff *skb,
+				   struct net_device *dev);
 static int epic_rx(struct net_device *dev, int budget);
 static int epic_poll(struct napi_struct *napi, int budget);
 static irqreturn_t epic_interrupt(int irq, void *dev_instance);
@@ -961,7 +962,7 @@
 	return;
 }
 
-static int epic_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t epic_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct epic_private *ep = netdev_priv(dev);
 	int entry, free_count;