hwmon: (ina238) Modify the calculation formula to adapt to different chips

Modify the calculation formula to adapt to different chips.

Signed-off-by: Wenliang Yan <wenliang202407@163.com>
Link: https://lore.kernel.org/r/20250506053741.4837-4-wenliang202407@163.com


[groeck: Fixed checkpatch issue (space before and after arithmetic operators)]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>