drivers: sensors: lsm6dsv16x: Fix bug in decoder

The lsm6dsv16x driver is using an incorrect value for the index
into the acceleration range. This results in using the wrong
range. The issue was found to be a bug in a MACRO in
lsm6dsv16x_decoder.h that was used to find the index in the
acceleration range. The MACRO was improperly counting zeros from the
leading edge, instead of the trailing edge.

Signed-off-by: Derek Valleroy <derekvalleroy@fb.com>