regulator: fix use after free bug

This is caused by dereferencing 'rdev' after device_unregister() in
the regulator_unregister() function.  'rdev' is freed by
device_unregister(), so it must not be dereferenced after this call.

[Edited commit message for legibility -- broonie]
Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/core.c

@@ -2799,8 +2799,8 @@ void regulator_unregister(struct regulator_dev *rdev)
 	list_del(&rdev->list);
 	if (rdev->supply)
 		regulator_put(rdev->supply);
-	device_unregister(&rdev->dev);
 	kfree(rdev->constraints);
+	device_unregister(&rdev->dev);
 	mutex_unlock(&regulator_list_mutex);
 }
 EXPORT_SYMBOL_GPL(regulator_unregister);