[clang] [llvm] [offload][OpenMP] Improve cross-team reduction grid selection (PR #208253)

[Dhruva Chakrabarti via cfe-commits]

dhruvachak wrote:

Re: The performance benefits I observed for the reduction tests in https://github.com/ro-i/xteam-test on a gfx942

What about other targets since they are impacted as well?

https://github.com/llvm/llvm-project/pull/208253