net: dsa: Add ndo_get_phys_port_name() for CPU port

There is not currently way to infer the port number through sysfs that
is being used as the CPU port number. Overlay a ndo_get_phys_port_name()
operation onto the DSA master network device in order to retrieve that
information.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dsa.h b/include/net/dsa.h
index b3eefe8..2f1daf2 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -208,6 +208,11 @@ struct dsa_port {
 	 * Original copy of the master netdev ethtool_ops
 	 */
 	const struct ethtool_ops *orig_ethtool_ops;
+
+	/*
+	 * Original copy of the master netdev net_device_ops
+	 */
+	const struct net_device_ops *orig_ndo_ops;
 };
 
 struct dsa_switch {