[clang] fix access checking about function overloading (PR #107768)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

This seems reasonable to me?  And passes tests?  

The `AS_none` has 'different meanings in different contexts, which is confusing here, so I have no idea what it is supposed to mean here.  But unless someone has a problem with this, I suspect we should just see what the fallout of this is...

THOUGH, because I'm not sure, perhaps we wait another ~week for the branch and only do this in Clang21+?

https://github.com/llvm/llvm-project/pull/107768