iio: Fix unitialized use of list

The dev_attr list is initialized in __iio_add_event_config_attrs which
is called only when indio_dev->channels is true. Nevertheless the list
is used unconditionally later in iio_device_register_eventset which
results in a NULL pointer exception. To fix this unconditionally
initialize the list in iio_device_register_eventset.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/industrialio-event.c

@@ -345,7 +345,6 @@ static inline int __iio_add_event_config_attrs(struct iio_dev *indio_dev)
 {
 	int j, ret, attrcount = 0;
 
-	INIT_LIST_HEAD(&indio_dev->event_interface->dev_attr_list);
 	/* Dynically created from the channels array */
 	for (j = 0; j < indio_dev->num_channels; j++) {
 		ret = iio_device_add_event_sysfs(indio_dev,
@@ -396,6 +395,8 @@ int iio_device_register_eventset(struct iio_dev *indio_dev)
 		goto error_ret;
 	}
 
+	INIT_LIST_HEAD(&indio_dev->event_interface->dev_attr_list);
+
 	iio_setup_ev_int(indio_dev->event_interface);
 	if (indio_dev->info->event_attrs != NULL) {
 		attr = indio_dev->info->event_attrs->attrs;