net: use symbolic values for ndo_start_xmit() return codes

Convert magic values 1 and -1 to NETDEV_TX_BUSY and NETDEV_TX_LOCKED respectively.

0 (NETDEV_TX_OK) is not changed to keep the noise down, except in very few cases
where its in direct proximity to one of the other values.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/plip.c b/drivers/net/plip.c
index 0be0f0b..7a62f78 100644
--- a/drivers/net/plip.c
+++ b/drivers/net/plip.c
@@ -955,12 +955,12 @@
 	struct plip_local *snd = &nl->snd_data;
 
 	if (netif_queue_stopped(dev))
-		return 1;
+		return NETDEV_TX_BUSY;
 
 	/* We may need to grab the bus */
 	if (!nl->port_owner) {
 		if (parport_claim(nl->pardev))
-			return 1;
+			return NETDEV_TX_BUSY;
 		nl->port_owner = 1;
 	}
 
@@ -969,7 +969,7 @@
 	if (skb->len > dev->mtu + dev->hard_header_len) {
 		printk(KERN_WARNING "%s: packet too big, %d.\n", dev->name, (int)skb->len);
 		netif_start_queue (dev);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	if (net_debug > 2)