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/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 921e533..cb7b247 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -4361,11 +4361,10 @@ static int mv88e6xxx_register_switch(struct mv88e6xxx_chip *chip)
 	struct device *dev = chip->dev;
 	struct dsa_switch *ds;
 
-	ds = devm_kzalloc(dev, sizeof(*ds), GFP_KERNEL);
+	ds = dsa_switch_alloc(dev, DSA_MAX_PORTS);
 	if (!ds)
 		return -ENOMEM;
 
-	ds->dev = dev;
 	ds->priv = chip;
 	ds->ops = &mv88e6xxx_switch_ops;