hwmon: (pmbus) Add driver for BluTek BPA-RS600

The BPA-RS600 is a compact 600W AC to DC removable power supply module.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210317040231.21490-3-chris.packham@alliedtelesis.co.nz


[groeck: Added bpa-rs600 to index.rst]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>