[llvm] [AArch64][SVE] Add partial reduction SDNodes (PR #117185)

[Benjamin Maxwell via llvm-commits]

================
@@ -1451,6 +1451,11 @@ enum NodeType {
   VECREDUCE_UMAX,
   VECREDUCE_UMIN,
 
+  // The `llvm.experimental.vector.partial.reduce.add` intrinsic
----------------
MacDue wrote:

nit:
```suggestion
  // This corresponds to the `llvm.experimental.vector.partial.reduce.add` intrinsic
```

https://github.com/llvm/llvm-project/pull/117185