hwmon: (pmbus) Add client driver for IR35221

IR35221 is a Digital DC-DC Multiphase Converter

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
[groeck: Preserve alphabetic order in Kconfig;
	add missing break statements (from Dan Carpenter);
	add missing error checks]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>