The reason of defining BMI160_MAX_FIFO_SAMPLES as 8 can be found on the
following histogram of the number of samples in the FIFO on each read while
performing the accelerometer calibration process:
Samples Count Freq Acc. Freq
------------------------------
1 3842 0.1201 0.120111
2 13172 0.4118 0.531904
3 9065 0.2834 0.815300
4 2710 0.0847 0.900022
5 2231 0.0697 0.969769
6 816 0.0255 0.995279
7 137 0.0043 0.999562
8 13 0.0004 0.999969
13 1 0.0000 1.000000