Fix Ethernet init() return codes

Change return values of init() functions in all Ethernet drivers to conform
to the following:

    >=0: Success
    <0:  Failure

All drivers going forward should return 0 on success.  Current drivers that
return 1 on success were left as-is to minimize changes.

Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
Acked-by: Stefan Roese <sr@denx.de>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Kim Phillips <kim.phillips@freescale.com>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-By: Timur Tabi <timur@freescale.com>
diff --git a/drivers/net/tsec.c b/drivers/net/tsec.c
index 108cebd..25392f6 100644
--- a/drivers/net/tsec.c
+++ b/drivers/net/tsec.c
@@ -232,7 +232,7 @@
 	startup_tsec(dev);
 
 	/* If there's no link, fail */
-	return priv->link;
+	return (priv->link ? 0 : -1);
 
 }