net: dsa: variable number of ports

Change the ports[DSA_MAX_PORTS] array of the dsa_switch structure for a
zero-length array, allocated at the same time as the dsa_switch
structure itself. A dsa_switch_alloc() helper is provided for that.

This commit brings no functional change yet since we pass DSA_MAX_PORTS
as the number of ports for the moment. Future patches can update the DSA
drivers separately to support dynamic number of ports.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index c084aa4..f67c6a3 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -954,12 +954,11 @@ qca8k_sw_probe(struct mdio_device *mdiodev)
 	if (id != QCA8K_ID_QCA8337)
 		return -ENODEV;
 
-	priv->ds = devm_kzalloc(&mdiodev->dev, sizeof(*priv->ds), GFP_KERNEL);
+	priv->ds = dsa_switch_alloc(&mdiodev->dev, DSA_MAX_PORTS);
 	if (!priv->ds)
 		return -ENOMEM;
 
 	priv->ds->priv = priv;
-	priv->ds->dev = &mdiodev->dev;
 	priv->ds->ops = &qca8k_switch_ops;
 	mutex_init(&priv->reg_mutex);
 	dev_set_drvdata(&mdiodev->dev, priv);