hwmon: (pmbus) Add Delta AHE-50DC fan control module driver

hwmon: (pmbus) Add Delta AHE-50DC fan control module driver

This device is an integrated module of the Delta AHE-50DC Open19 power
shelf.  I haven't been able to procure any proper documentation for
it, but it seems to be a (somewhat minimally) PMBus-compliant device.
It provides four fan speeds, four temperatures (three standard and one
manufacturer-specific via a virtual second page), and a vin reading.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Link: https://lore.kernel.org/r/20211208213703.2577-2-zev@bewilderbeest.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>