iio: dummy: iio_simple_dummy_buffer: Demote file header and correct misspelling

File headers are not good candidates for kerneldoc.

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

 drivers/iio/dummy/iio_simple_dummy_buffer.c:27: warning: cannot understand function prototype: 'const s16 fakedata[] = '
 drivers/iio/dummy/iio_simple_dummy_buffer.c:185: warning: Function parameter or member 'indio_dev' not described in 'iio_simple_dummy_unconfigure_buffer'
 drivers/iio/dummy/iio_simple_dummy_buffer.c:185: warning: Excess function parameter 'indo_dev' description in 'iio_simple_dummy_unconfigure_buffer'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dummy/iio_simple_dummy_buffer.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (c) 2011 Jonathan Cameron
  *
  * Buffer handling elements of industrial I/O reference driver.
@@ -165,7 +165,7 @@ int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 
 /**
  * iio_simple_dummy_unconfigure_buffer() - release buffer resources
- * @indo_dev: device instance state
+ * @indio_dev: device instance state
  */
 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
 {