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/atl1c/atl1c_main.c b/drivers/net/atl1c/atl1c_main.c
index 1d601ce..bf7cc83 100644
--- a/drivers/net/atl1c/atl1c_main.c
+++ b/drivers/net/atl1c/atl1c_main.c
@@ -2055,7 +2055,8 @@
 	AT_WRITE_REG(&adapter->hw, REG_MB_PRIO_PROD_IDX, prod_data);
 }
 
-static int atl1c_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
+static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
+					  struct net_device *netdev)
 {
 	struct atl1c_adapter *adapter = netdev_priv(netdev);
 	unsigned long flags;