[clang] [Clang][AMDGPU] Stop defaulting to `one-as` for all atomic scopes (PR #120095)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

> This one-as business seems like it's cruft from before MMRAs. Can we rip them out and replace them with MMRAs for OpenCL?

https://llvm.org/docs/MemoryModelRelaxationAnnotations.html calls out the opencl fence as a motivating example which suggests either yes, or we should amend the MMRA system to be able to express it. Sounds like a much cleaner fix to me, but also open to unblocking openmp with an "if (opencl) {}" clause in the meantime.

https://github.com/llvm/llvm-project/pull/120095