[llvm] [LoopVectorize] Fix double-application of FindIV reduction expression in epilogue (PR #219362)

[via llvm-commits]

im-lunex wrote:

@fhahn I tested the issue reproducer on the upstream(main), and this doesn't crash anymore... so we can say this issue is already fixed in the current upstream...

https://github.com/llvm/llvm-project/pull/219362