[llvm] [SimplifyCFG] Updated early exit in `CanRedirectPredsOfEmptyBBToSucc` (PR #142582)

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kper wrote:

> The goal is that for.inc295 gets merged to for.end297 since it only contains an unconditional jump.

I was not able to get that done. I would have had multiple values from the same bb and I am not sure whether that would be correct. So I just focused on not having the infinity loop.

I've added a check when no values have been redirected then `return false`. I had to update a few more tests. In some cases, it just reordered the phi values. I hope that's ok.

https://github.com/llvm/llvm-project/pull/142582