ACPI / scan: Fix acpi_bus_id_list bookkeeping

acpi_device_add() allocates and adds an element to acpi_bus_id_list
(or increments the instance count if the device's HID is already
present in the list), but the element is never deleted from the list
nor freed. Fix it.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/scan.c

@@ -471,10 +471,24 @@ static void acpi_device_release(struct device *dev)
 
 static void acpi_device_del(struct acpi_device *device)
 {
+	struct acpi_device_bus_id *acpi_device_bus_id;
+
 	mutex_lock(&acpi_device_lock);
 	if (device->parent)
 		list_del(&device->node);
 
+	list_for_each_entry(acpi_device_bus_id, &acpi_bus_id_list, node)
+		if (!strcmp(acpi_device_bus_id->bus_id,
+			    acpi_device_hid(device))) {
+			if (acpi_device_bus_id->instance_no > 0)
+				acpi_device_bus_id->instance_no--;
+			else {
+				list_del(&acpi_device_bus_id->node);
+				kfree(acpi_device_bus_id);
+			}
+			break;
+		}
+
 	list_del(&device->wakeup_list);
 	mutex_unlock(&acpi_device_lock);