If your Adsense integration is purely client-side (using the javascript snippet from Adsense), then Cloudflare isn't a factor. The javascript library will fetch its data from Adsense directly through the visitor's web access and won't be aware the page was served through a proxy.
I'm not aware of any server-side Adsense integration existence, but if that existed you would probably need to make sure you are feeding that module with the correct upstream IP address and user agent.
