[llvm] [SelectionDAG] Add PARTIAL_REDUCE_U/SMLA ISD Nodes (PR #125207)

[Sander de Smalen via llvm-commits]

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@@ -1451,6 +1451,19 @@ enum NodeType {
   VECREDUCE_UMAX,
   VECREDUCE_UMIN,
 
+  // PARTIAL_REDUCE_[U|S]MLA(Accumulator, Input1, Input2)
+  // The partial reduction nodes sign-or zero extend Input1 and Input2 to
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sdesmalen-arm wrote:

minor nit:
```suggestion
  // The partial reduction nodes sign- or zero extend Input1 and Input2 to
```

https://github.com/llvm/llvm-project/pull/125207