net: dsa: better error reporting

Add additional error reporting to the generic DSA code, so it's easier
to debug when things go wrong.  This was useful when initially bringing
up 88e6176 on a new board.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index c59fa5d..aa398bc 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -326,8 +326,8 @@
 
 		ret = dsa_slave_create(ds, parent, i, pd->port_names[i]);
 		if (ret < 0) {
-			netdev_err(dst->master_netdev, "[%d]: can't create dsa slave device for port %d(%s)\n",
-				   index, i, pd->port_names[i]);
+			netdev_err(dst->master_netdev, "[%d]: can't create dsa slave device for port %d(%s): %d\n",
+				   index, i, pd->port_names[i], ret);
 			ret = 0;
 		}
 	}