[clang] [Clang] Fix sret AS for non-trivial-copy returns. (PR #186275)

[Alex Voicu via cfe-commits]

AlexVlx wrote:

@VigneshwarJ could you please extend the tests to also verify `spirv64-amd-amdhsa` i.e. AMDGCNSPIRV? That has a non-zero default AS and a slightly different AS map in general, which has traditionally been a bug farm.

https://github.com/llvm/llvm-project/pull/186275