While the chips supported by this driver do not directly support current
limits, they do support setting shunt voltage limits. The shunt voltage
divided by the shunt resistor value is the current. On top of that,
calibration values are set such that in the shunt voltage register and
the current register report the same values. That means we can report and
configure current limits based on shunt voltage limits, and we can do so
with much better accuracy than by setting shunt voltage limits.