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>
diff --git a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
index 7a525a9..87419c4 100644
--- a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
+++ b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
@@ -31,7 +31,7 @@
 static int hid_sensor_data_rdy_trigger_set_state(struct iio_trigger *trig,
 						bool state)
 {
-	struct hid_sensor_common *st = trig->private_data;
+	struct hid_sensor_common *st = iio_trigger_get_drvdata(trig);
 	int state_val;
 
 	state_val = state ? 1 : 0;
@@ -76,7 +76,7 @@
 	}
 
 	trig->dev.parent = indio_dev->dev.parent;
-	trig->private_data = attrb;
+	iio_trigger_set_drvdata(trig, attrb);
 	trig->ops = &hid_sensor_trigger_ops;
 	ret = iio_trigger_register(trig);