[clang] [AMDGPU] Enable overriding of OpenCL's default address space (PR #117588)

[Alex Voicu via cfe-commits]

AlexVlx wrote:

Thank you for this, unfortunately I don't quite see the reason for adding another twiddly bit here. We are long term migrating away from the default-is-private hack, and to get the benefits you are looking for you can simply compile for CL2, or enable the generic as extension, for which there are already defined mechanisms.

https://github.com/llvm/llvm-project/pull/117588