Ryzen Master just released 2287 which "Adds support for setting Maximum Temperature". I have installed it on my old 3970X and have not found the option yet but that may be because the new feature is not supported on my old processor. I hope someone will try 2287 on a new Ryzen and report. Enjoy, John.
AMD Support explained how to use this. My old processor (3970X) does not support this but I was curious what values are supported in the pull down list. My BIOS does support setting the maximum temperature under the PBO settings, but it did not seem to do anything.
Please post a screenshot of the list. It may allow only lowering of the temperature. Thanks and enjoy, John.