Input: twl6040-vibra - fix NULL pointer dereference by removing workqueue

commit 21fb9f0d ("Input: twl6040-vibra - use system workqueue")

says that it switches to use the system workqueue but it did neither

- remove the workqueue struct variable
- replace code to really use the system workqueue

Instead it calls queue_work() on uninitialized info->workqueue.

The result is a NULL pointer dereference in vibra_play().

Solution: use schedule_work
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/twl6040-vibra.c

@@ -45,7 +45,6 @@
 struct vibra_info {
 	struct device *dev;
 	struct input_dev *input_dev;
-	struct workqueue_struct *workqueue;
 	struct work_struct play_work;
 	struct mutex mutex;
 	int irq;
@@ -213,7 +212,7 @@ static int vibra_play(struct input_dev *input, void *data,
 	info->strong_speed = effect->u.rumble.strong_magnitude;
 	info->direction = effect->direction < EFFECT_DIR_180_DEG ? 1 : -1;
 
-	ret = queue_work(info->workqueue, &info->play_work);
+	ret = schedule_work(&info->play_work);
 	if (!ret) {
 		dev_info(&input->dev, "work is already on queue\n");
 		return ret;