hwmon: (mr75203) add debugfs to read and write temperature coefficients

hwmon: (mr75203) add debugfs to read and write temperature coefficients

This change adds debugfs to read and write temperature sensor coefficients
- g, h, j and cal5.

The coefficients can vary between product and product, so it can be very
useful to be able to modify them on the fly during the calibration
process.

e.g.:

cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_cal5
4096

echo 83000 > sys/kernel/debug/940f23d0000.pvt/ts_coeff_g

Signed-off-by: Eliav Farber <farbere@amazon.com>
Link: https://lore.kernel.org/r/20220908152449.35457-21-farbere@amazon.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>