hwmon: pmbus: Add Inspur Power System power supply driver

Add the driver to monitor Inspur Power System power supplies
with hwmon over pmbus.

This driver adds sysfs attributes for additional power supply data,
including vendor, model, part_number, serial number,
firmware revision, hardware revision, and psu mode(active/standby).

Signed-off-by: John Wang <wangzqbj@inspur.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20190819091509.29276-1-wangzqbj@inspur.com


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