[llvm] [MemProf] Fix when CallStackTrie is a single chain with multi alloc type (PR #79433)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

> > I had a suggestion on the PR.
> 
> Sorry, I don't quite understand. What is your suggestion?

Woops, still getting used to the PR interface. The comment was left as pending and should have been sent now.

https://github.com/llvm/llvm-project/pull/79433