hwmon: (ina238) Improve current dynamic range

hwmon: (ina238) Improve current dynamic range

The best possible dynamic range for current measurements is achieved
if the shunt register value matches the current register value. Adjust
the calibration register as well as fixed and default shunt resistor
values accordingly to achieve this range.

Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz> # INA780
Signed-off-by: Guenter Roeck <linux@roeck-us.net>