iio: imu: st_lsmdsx: compact st_lsm6dsx_sensor_settings table

Shrink st_lsm6dsx_sensor_settings table size moving wai address info in
id array and remove duplicated code

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/c43286938b2fe03ab3abdb5fc095ea6b950abcb1.1606557946.git.lorenzo@kernel.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>