sensor: lis2dux12: fix SENSOR_ATTR_FULL_SCALE case

When setting the full scale through SENSOR_ATTR_FULL_SCALE the
driver must convert the g value (i.e. one of 2g/4g/8g/16g) to
the corrispondent sensor fs raw value.

Signed-off-by: Armando Visconti <armando.visconti@st.com>
(cherry picked from commit 2eaec8b7)