generic: ar8216: fix invalid bounds check imported from ChromeOS (FS#347)

The priv->vlan_id member is of size AR8X16_MAX_VLANS, not AR8X16_MAX_PORTS,
so check for the proper maximum value in order to avoid capping valid VLAN IDs
to 7 (AR8X16_MAX_PORTS - 1).

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

target/linux/generic/files/drivers/net/phy/ar8216.c

@@ -975,7 +975,7 @@ ar8xxx_sw_set_vid(struct switch_dev *dev, const struct switch_attr *attr,
 {
 	struct ar8xxx_priv *priv = swdev_to_ar8xxx(dev);
 
-	if (val->port_vlan >= AR8X16_MAX_PORTS)
+	if (val->port_vlan >= AR8X16_MAX_VLANS)
 		return -EINVAL;
 
 	priv->vlan_id[val->port_vlan] = val->value.i;