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/forcedeth.c b/drivers/net/forcedeth.c
index 3b4e076..0a1c2bb 100644
--- a/drivers/net/forcedeth.c
+++ b/drivers/net/forcedeth.c
@@ -2137,7 +2137,7 @@
  * nv_start_xmit: dev->hard_start_xmit function
  * Called with netif_tx_lock held.
  */
-static int nv_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t nv_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct fe_priv *np = netdev_priv(dev);
 	u32 tx_flags = 0;
@@ -2257,7 +2257,8 @@
 	return NETDEV_TX_OK;
 }
 
-static int nv_start_xmit_optimized(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t nv_start_xmit_optimized(struct sk_buff *skb,
+					   struct net_device *dev)
 {
 	struct fe_priv *np = netdev_priv(dev);
 	u32 tx_flags = 0;