iio: adc: ti-adc084s021: kernel-doc fixes, missing function names

The documentation in this driver was nearly kernel-doc and was marked
as such. Unfortunately the format was wrong and function names were
missing. This patch puts them in with minor edits to keep the resulting
line short.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Gwendal Grignou <gwendal@chromium.org>
Cc: Mårten Lindahl <martenli@axis.com>
Link: https://lore.kernel.org/r/20210314164655.408461-3-jic23@kernel.org