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

[Philip Reames via llvm-commits]

preames wrote:

Alexey, can I get an LGTM?  If possible, I'd like to get this in before you continue your whole register line of patches, those have been causing significant rebase pain.

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