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/sb1000.c b/drivers/net/sb1000.c
index 6a81aec..ee366c5 100644
--- a/drivers/net/sb1000.c
+++ b/drivers/net/sb1000.c
@@ -82,7 +82,8 @@
 extern int sb1000_probe(struct net_device *dev);
 static int sb1000_open(struct net_device *dev);
 static int sb1000_dev_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd);
-static int sb1000_start_xmit(struct sk_buff *skb, struct net_device *dev);
+static netdev_tx_t sb1000_start_xmit(struct sk_buff *skb,
+				     struct net_device *dev);
 static irqreturn_t sb1000_interrupt(int irq, void *dev_id);
 static int sb1000_close(struct net_device *dev);
 
@@ -1080,7 +1081,7 @@
 }
 
 /* transmit function: do nothing since SB1000 can't send anything out */
-static int
+static netdev_tx_t
 sb1000_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	printk(KERN_WARNING "%s: trying to transmit!!!\n", dev->name);