net: dsa: Add a ports structure and use it in the switch structure

There are going to be more per-port members added to the switch
structure. So add a port structure and move the netdev into it.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index f640a48..169abac 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1183,12 +1183,12 @@
 	p->old_link = -1;
 	p->old_duplex = -1;
 
-	ds->ports[port] = slave_dev;
+	ds->ports[port].netdev = slave_dev;
 	ret = register_netdev(slave_dev);
 	if (ret) {
 		netdev_err(master, "error %d registering interface %s\n",
 			   ret, slave_dev->name);
-		ds->ports[port] = NULL;
+		ds->ports[port].netdev = NULL;
 		free_netdev(slave_dev);
 		return ret;
 	}