hwmon: (nct6775) Add i2c driver

hwmon: (nct6775) Add i2c driver

This driver provides an i2c I/O mechanism for the core nct6775 driver,
as might be used by a BMC.  Because the Super I/O chip is shared with
the host CPU in such a scenario (and the host should ultimately be in
control of it), the i2c driver is strictly read-only to avoid
interfering with any usage by the host (aside from the bank-select
register, which seems to be replicated for the i2c interface).

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Tested-by: Renze Nicolai <renze@rnplus.nl>
Link: https://lore.kernel.org/r/20220428012707.24921-3-zev@bewilderbeest.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>