[llvm] [SPIRV] Add missing OpenCL atomic_fetch_min/max builtin mappings (PR #190443)

[Marcos Maronas via llvm-commits]

https://github.com/maarquitos14 approved this pull request.

Overall LGTM, just a question: you mention __spirv_Atomic{S,U}{Min,Max} in the PR description. Should we also add them to the test, or to a new test? Or are they already tested in an existing test?

https://github.com/llvm/llvm-project/pull/190443