[clang] [AMDGPU] Allow w64 ballot to be used on w32 targets (PR #80183)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> After this change is there any value in having two different builtins? You could just have one that always return 64 bits.

I personally think it would be better to just have the one, but I figured that decision was made earlier and it would break backwards compatibility.

https://github.com/llvm/llvm-project/pull/80183