hwmon: (nct6775) Split core and platform driver

This splits the nct6775 driver into an interface-independent core and
a separate platform driver that wraps inb/outb port I/O (or asuswmi
methods) around that core.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Tested-by: Renze Nicolai <renze@rnplus.nl>
Link: https://lore.kernel.org/r/20220427010154.29749-7-zev@bewilderbeest.net
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>