[llvm] [SimplifyCFG] Skip threading if the target may have divergent branches (PR #100185)

[via llvm-commits]

ronlieb wrote:

in addition to breaks HIP buildbot, unanswered review comments, merged without approval i am seeing downstream aborts in gpu code due to this patch. 

plz revert it. 

https://github.com/llvm/llvm-project/pull/100185