[clang] [CIR][SPIR-V] Split SPIR and SPIR-V target lowering to keep atomic sync scopes (PR #231754)

[Arseniy Obolenskiy via cfe-commits]

aobolensk wrote:

> Could you please update the title and description to reflect the split?

Updated, thanks

https://github.com/llvm/llvm-project/pull/231754