iio: accel: iis328dq: fix gain values

iio: accel: iis328dq: fix gain values

The sensors IIS328DQ and H3LIS331DL share one configuration but
H3LIS331DL has different gain parameters, configs therefore
need to be split up.
The gain parameters for the IIS328DQ are 0.98, 1.95 and 3.91,
depending on the selected measurement range.

See sensor manuals, chapter 2.1 "mechanical characteristics",
parameter "Sensitivity".

Datasheet: https://www.st.com/resource/en/datasheet/iis328dq.pdf
Datasheet: https://www.st.com/resource/en/datasheet/h3lis331dl.pdf
Fixes: 46e33707fe95 ("iio: accel: add support for IIS328DQ variant")
Reviewed-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
Signed-off-by: Markus Koeniger <markus.koeniger@liebherr.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>