[llvm] [RISCV] Convert vector.reduce.or + cttz.elts to vfirst (PR #175952)

[Craig Topper via llvm-commits]

topperc wrote:

Why does the vectorizer use get.active.lane.mask instead of using vp.reduce.or and llvm.vp.cttz.elts?

https://github.com/llvm/llvm-project/pull/175952