dt-bindings: hwmon: (mr75203) add description for Moortec's PVT controller

This changes adds a detailed description for the mr75203 controller and
for some of the analog IPs controlled by it.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220908152449.35457-8-farbere@amazon.com


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