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/tokenring/tms380tr.c b/drivers/net/tokenring/tms380tr.c
index b11bb72..a2eab72 100644
--- a/drivers/net/tokenring/tms380tr.c
+++ b/drivers/net/tokenring/tms380tr.c
@@ -633,7 +633,7 @@
 		if (tms380tr_debug > 0)
 			printk(KERN_DEBUG "%s: No free TPL\n", dev->name);
 		spin_unlock_irqrestore(&tp->lock, flags);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	dmabuf = 0;