[llvm] [SLP] Enable reordering for non-power-of-two vectors (PR #106638)

[Philip Reames via llvm-commits]

preames wrote:

> Please rebase

I have asked for a revert of the change causing the bad merge, please see: https://github.com/llvm/llvm-project/pull/106449

https://github.com/llvm/llvm-project/pull/106638