[llvm] [SLP] Exit early if MaxVF < MinVF (NFCI). (PR #83283)

[Florian Hahn via llvm-commits]

fhahn wrote:

> Hmm, I don't think this is NFC, would be good to have a test

Yes I think technically this could change dbg output. Let me add a test for that.

https://github.com/llvm/llvm-project/pull/83283