[clang] clang: Simplify emission of uniform-work-group-size attribute (PR #185066)

[Artem Belevich via cfe-commits]

https://github.com/Artem-B commented:

LGTM in principle, but I'm not familiar with OCL to tell what effect annotation of all functions will have, so just editorial nits on pre-existing comment from me. Feel free to ignore those.

https://github.com/llvm/llvm-project/pull/185066