hwmon: pmbus: mpq8785: Implement VOUT feedback resistor divider ratio configuration

hwmon: pmbus: mpq8785: Implement VOUT feedback resistor divider ratio configuration

Implement support for setting the VOUT_SCALE_LOOP PMBus register
based on an optional device tree property
"mps,vout-fb-divider-ratio-permille".

This allows the driver to provide the correct VOUT value depending
on the feedback voltage divider configuration for chips where the
bootloader does not configure the VOUT_SCALE_LOOP register.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Link: https://lore.kernel.org/r/20250511035701.2607947-4-paweldembicki@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>