[llvm] [Statepoint] Return undef value for the statepoint of the none token (PR #72552)

[Nuno Lopes via llvm-commits]

nunoplopes wrote:

Can you use poison here?
We are trying to get rid of undef, so if this can use poison today, it would help the effort.
Thank you!

https://github.com/llvm/llvm-project/pull/72552