net: dsa: add ds and index to dsa_port

Add the physical switch instance and port index a DSA port belongs to to
the dsa_port structure.

That can be used later to retrieve information about a physical port
when configuring a switch fabric, or lighten up struct dsa_slave_priv.

Signed-off-by: Vivien Didelot <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/dsa.h

···
 };
 
 struct dsa_port {
+	struct dsa_switch	*ds;
+	unsigned int		index;
 	struct net_device	*netdev;
 	struct device_node	*dn;
 	unsigned int		ageing_time;

net/dsa/dsa2.c

···
 {
 	size_t size = sizeof(struct dsa_switch) + n * sizeof(struct dsa_port);
 	struct dsa_switch *ds;
+	int i;
 
 	ds = devm_kzalloc(dev, size, GFP_KERNEL);
 	if (!ds)
···
 
 	ds->dev = dev;
 	ds->num_ports = n;
+
+	for (i = 0; i < ds->num_ports; ++i) {
+		ds->ports[i].index = i;
+		ds->ports[i].ds = ds;
+	}
 
 	return ds;
 }