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/bnx2x_main.c b/drivers/net/bnx2x_main.c
index b318d16..e2e5026 100644
--- a/drivers/net/bnx2x_main.c
+++ b/drivers/net/bnx2x_main.c
@@ -10936,7 +10936,7 @@
  * bnx2x_tx_int() runs without netif_tx_lock unless it needs to call
  * netif_wake_queue()
  */
-static int bnx2x_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t bnx2x_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct bnx2x *bp = netdev_priv(dev);
 	struct bnx2x_fastpath *fp, *fp_stat;