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/enc28j60.c b/drivers/net/enc28j60.c
index 372d6c6..117fc6c 100644
--- a/drivers/net/enc28j60.c
+++ b/drivers/net/enc28j60.c
@@ -1276,7 +1276,8 @@
 	locked_reg_bfset(priv, ECON1, ECON1_TXRTS);
 }
 
-static int enc28j60_send_packet(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t enc28j60_send_packet(struct sk_buff *skb,
+					struct net_device *dev)
 {
 	struct enc28j60_net *priv = netdev_priv(dev);