[llvm] Add support for single reductions in ComplexDeinterleavingPass (PR #112875)

[antoine moynault via llvm-commits]

antmox wrote:

Also causing same failures here : 
https://lab.llvm.org/buildbot/#/builders/198/builds/334
https://lab.llvm.org/buildbot/#/builders/143/builds/4276
https://lab.llvm.org/buildbot/#/builders/17/builds/4725

https://github.com/llvm/llvm-project/pull/112875