Revert "[CostModel] remove cost-kind predicate for vector reduction costs"

This reverts commit 22d10b8a.

This broke compilation e.g. like this:
$ cat synth.c
*a;
float *b;
c() {
  for (;;) {
    float d = -*b * *a++;
    d -= *--b * *a++;
    d -= *--b * *a;
    d -= *--b * *a;
    e(d);
  }
}
$ clang -target x86_64-linux-gnu -c -O2 -ffast-math synth.c
clang: ../include/llvm/Support/Casting.h:104: static bool llvm::isa_impl
_cl<To, const From*>::doit(const From*) [with To = llvm::PointerType; Fr
om = llvm::Type]: Assertion `Val && "isa<> used on a null pointer"' fail
ed.