Fix mlir windows buildbot after ec146cb7

ec146cb7 added two new ReducKinds for float maximum and minimum
(along with support in loop vectorizer).

Enumerate these kinds in SLPVectorizer to fix mlir windows build bot
errors:

C:\buildbot\mlir-x64-windows-ninja\llvm-project\llvm\lib\Transforms\Vectorize\SLPVectorizer.cpp(13883): error C2220: the following warning is treated as an error
C:\buildbot\mlir-x64-windows-ninja\llvm-project\llvm\lib\Transforms\Vectorize\SLPVectorizer.cpp(13883): warning C4062: enumerator 'llvm::RecurKind::FMinimum' in switch of enum 'llvm::RecurKind' is not handled