[llvm] [IR] Add elementwise modifier to atomic loads (PR #204556)

[Harrison Hao via llvm-commits]

harrisonGPU wrote:

> I think it probably would have been better to wait for the clarification, as you've merged it currently you are accepting `seq_cst` for elementwise atomic loads and stores, whereas the consensus seems to be that we don't want to allow it. I'll fix it in my PR.

Okay, thanks, really appreciate.

https://github.com/llvm/llvm-project/pull/204556