iio: dummy: iio_simple_dummy_events: Demote file header and supply descriptions for val2 params

File headers are not good candidates for kerneldoc.

Fixes the following W=1 kernel build warning(s):

 drivers/iio/dummy/iio_simple_dummy_events.c:21: warning: Incorrect use of kernel-doc format:  * iio_simple_dummy_read_event_config() - is event enabled?
 drivers/iio/dummy/iio_simple_dummy_events.c:34: warning: Function parameter or member 'indio_dev' not described in 'iio_simple_dummy_read_event_config'
 drivers/iio/dummy/iio_simple_dummy_events.c:34: warning: Function parameter or member 'chan' not described in 'iio_simple_dummy_read_event_config'
 drivers/iio/dummy/iio_simple_dummy_events.c:34: warning: Function parameter or member 'type' not described in 'iio_simple_dummy_read_event_config'
 drivers/iio/dummy/iio_simple_dummy_events.c:34: warning: Function parameter or member 'dir' not described in 'iio_simple_dummy_read_event_config'
 drivers/iio/dummy/iio_simple_dummy_events.c:123: warning: Function parameter or member 'val2' not described in 'iio_simple_dummy_read_event_value'
 drivers/iio/dummy/iio_simple_dummy_events.c:146: warning: Function parameter or member 'val2' not described in 'iio_simple_dummy_write_event_value'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dummy/iio_simple_dummy_events.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (c) 2011 Jonathan Cameron
  *
  * Event handling elements of industrial I/O reference driver.
@@ -107,6 +107,7 @@ int iio_simple_dummy_write_event_config(struct iio_dev *indio_dev,
  * @dir: direction of the vent whose value is being read
  * @info: info type of the event whose value is being read
  * @val: value for the event code.
+ * @val2: unused
  *
  * Many devices provide a large set of events of which only a subset may
  * be enabled at a time, with value registers whose meaning changes depending
@@ -136,6 +137,7 @@ int iio_simple_dummy_read_event_value(struct iio_dev *indio_dev,
  * @dir: direction of the vent whose value is being set
  * @info: info type of the event whose value is being set
  * @val: the value to be set.
+ * @val2: unused
  */
 int iio_simple_dummy_write_event_value(struct iio_dev *indio_dev,
 				       const struct iio_chan_spec *chan,