dt-bindings: add Delta AHE-50DC fan control module

This is the integrated fan control module of the Delta AHE-50DC Open19
power shelf.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211208213703.2577-3-zev@bewilderbeest.net


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