[llvm] [SLP][REVEC] Make GetMinMaxCost support FixedVectorType when REVEC is enabled. (PR #115417)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

Thank you for updating the patch!  I don't know about its correctness, but it does pass `check-llvm` in my environment.

https://github.com/llvm/llvm-project/pull/115417