iio:trigger: Use dev_{set,get}_drvdata for private data management

Use dev_{set,get}_drvdata for managing private data attached to a trigger
instead of using a custom field in the iio_trigger struct.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/Documentation/trigger.txt

@@ -10,9 +10,6 @@ struct iio_trig *trig = iio_trigger_alloc("<trigger format string>", ...);
 allocates a trigger structure.  The key elements to then fill in within
 a driver are:
 
-trig->private_data
-	Device specific private data.
-
 trig->owner
 	Typically set to THIS_MODULE. Used to ensure correct
 	ownership of core allocated resources.

include/linux/iio/trigger.h

@@ -44,7 +44,6 @@ struct iio_trigger_ops {
  * @id:			[INTERN] unique id number
  * @name:		[DRIVER] unique name
  * @dev:		[DRIVER] associated device (if relevant)
- * @private_data:	[DRIVER] device specific data
  * @list:		[INTERN] used in maintenance of global trigger list
  * @alloc_list:		[DRIVER] used for driver specific trigger list
  * @use_count:		use count for the trigger
@@ -60,7 +59,6 @@ struct iio_trigger {
 	const char			*name;
 	struct device			dev;
 
-	void				*private_data;
 	struct list_head		list;
 	struct list_head		alloc_list;
 	int use_count;
@@ -101,7 +99,7 @@ static inline void iio_trigger_get(struct iio_trigger *trig)
  */
 static inline void iio_trigger_set_drvdata(struct iio_trigger *trig, void *data)
 {
-	trig->private_data = data;
+	dev_set_drvdata(&trig->dev, data);
 }
 
 /**
@@ -112,7 +110,7 @@ static inline void iio_trigger_set_drvdata(struct iio_trigger *trig, void *data)
  */
 static inline void *iio_trigger_get_drvdata(struct iio_trigger *trig)
 {
-	return trig->private_data;
+	return dev_get_drvdata(&trig->dev);
 }
 
 /**