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/rrunner.h b/drivers/net/rrunner.h
index 6173f11..2816904 100644
--- a/drivers/net/rrunner.h
+++ b/drivers/net/rrunner.h
@@ -831,7 +831,8 @@
 static irqreturn_t rr_interrupt(int irq, void *dev_id);
 
 static int rr_open(struct net_device *dev);
-static int rr_start_xmit(struct sk_buff *skb, struct net_device *dev);
+static netdev_tx_t rr_start_xmit(struct sk_buff *skb,
+				 struct net_device *dev);
 static int rr_close(struct net_device *dev);
 static int rr_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
 static unsigned int rr_read_eeprom(struct rr_private *rrpriv,