bma4xx: Optimize calculation

Reduce some of the arithmetic required to decode a sample. Math is
documented in bma4xx_convert_raw_accel_to_q31.

This improved the accuracy from roughly 0.865mm/s2 to 0.001mm/s2 when
stationary and using a range of 4g.

Signed-off-by: Yuval Peress <peress@google.com>
1 file changed