smsc75xx: add more information to register io failure warnings

Signed-off-by: Stephane Fillod <fillods@users.sf.net>
Signed-off-by: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/smsc75xx.c b/drivers/net/usb/smsc75xx.c
index f97207a..1de7785 100644
--- a/drivers/net/usb/smsc75xx.c
+++ b/drivers/net/usb/smsc75xx.c
@@ -98,7 +98,7 @@
 
 	if (unlikely(ret < 0))
 		netdev_warn(dev->net,
-			"Failed to read register index 0x%08x", index);
+			"Failed to read reg index 0x%08x: %d", index, ret);
 
 	le32_to_cpus(buf);
 	*data = *buf;
@@ -128,7 +128,7 @@
 
 	if (unlikely(ret < 0))
 		netdev_warn(dev->net,
-			"Failed to write register index 0x%08x", index);
+			"Failed to write reg index 0x%08x: %d", index, ret);
 
 	kfree(buf);