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

[Matt Arsenault via cfe-commits]

arsenm wrote:

> @b-sumner has useful context on this. I'll try not to speak for him but it sounds like the block deleted here has the right semantics for opencl, where "seqcst" has some special meaning and generally the semantics don't totally make sense to me. Suggest we amend this to "if opencl, do this thing, otherwise leave it alone"

I'd rather not infect this with poorly understood language based logic. The one-as should be more aggressive and safe to ignore.

> (can't see how to remove the green tick from the review)

"Request changes"

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