hwmon: (pmbus) Add support for pli1209bc

PLI1209BC is a Digital Supervisor from Vicor Corporation.

Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
Link: https://lore.kernel.org/r/4e016e66275bc46c90974aec18b150c874e64787.1645435888.git.sylv@sylv.io


Signed-off-by: Guenter Roeck <linux@roeck-us.net>