ACPI / thermal: fix workqueue destroy order

When the thermal module is to be removed, we should destroy the wq
acpi_thermal_pm_queue after the ACPI driver's remove callback is
executed as we will need to flush the workqueue there, or a NULL pointer
access will be hit.

Reported-and-tested-by: Kui Zhang <[e-mail]>
References: http://www.spinics.net/lists/kernel/msg1747251.html
Cc: All applicable <[e-mail]>
Signed-off-by: Aaron Lu <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/thermal.c

···
 
 static void __exit acpi_thermal_exit(void)
 {
-	destroy_workqueue(acpi_thermal_pm_queue);
 	acpi_bus_unregister_driver(&acpi_thermal_driver);
+	destroy_workqueue(acpi_thermal_pm_queue);
 
 	return;
 }