[AArch64] Improve codegen for partial.reduce.add v16i8 -> v2i32#161833

sdesmalen-arm merged 4 commits intollvm:mainllvm/llvm-project:mainfrom

sdesmalen-arm:improve-partial-reduce-v2i32sdesmalen-arm/llvm-project:improve-partial-reduce-v2i32Copy head branch name to clipboard