iio:trigger: Introduce iio_tigger_{set,get}_drvdata

Introduce iio_tigger_{set,get}_drvdata which allows to attach driver specific
data to a trigger. The functions wrap access to the triggers private_data field
and all current users are updated to use iio_tigger_{set,get}_drvdata instead of
directly accessing the private_data field. This is the first step towards
removing the private_data field from the iio_trigger struct.

The following coccinelle script has been used to update the drivers:
<smpl>
@@
struct iio_trigger *trigger;
expression priv;
@@
-trigger->private_data = priv
+iio_trigger_set_drv_data(trigger, priv)

@@
struct iio_trigger *trigger;
@@
-trigger->private_data
+iio_trigger_get_drv_data(trigger)
</smpl>

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/iio/trigger.h

@@ -91,6 +91,30 @@ static inline void iio_trigger_get(struct iio_trigger *trig)
 	__module_get(trig->ops->owner);
 }
 
+/**
+ * iio_device_set_drvdata() - Set trigger driver data
+ * @trig: IIO trigger structure
+ * @data: Driver specific data
+ *
+ * Allows to attach an arbitrary pointer to an IIO trigger, which can later be
+ * retrieved by iio_trigger_get_drvdata().
+ */
+static inline void iio_trigger_set_drvdata(struct iio_trigger *trig, void *data)
+{
+	trig->private_data = data;
+}
+
+/**
+ * iio_trigger_get_drvdata() - Get trigger driver data
+ * @trig: IIO trigger structure
+ *
+ * Returns the data previously set with iio_trigger_set_drvdata()
+ */
+static inline void *iio_trigger_get_drvdata(struct iio_trigger *trig)
+{
+	return trig->private_data;
+}
+
 /**
  * iio_trigger_register() - register a trigger with the IIO core
  * @trig_info:	trigger to be registered