[llvm] Add `llvm.vector.partial.reduce.fadd` intrinsic (PR #159776)

[Sander de Smalen via llvm-commits]

================
@@ -13113,8 +13139,12 @@ SDValue DAGCombiner::foldPartialReduceAdd(SDNode *N) {
           TLI.getTypeToTransformTo(*Context, UnextOp1VT)))
     return SDValue();
 
+  auto Constant = N->getOpcode() == ISD::PARTIAL_REDUCE_FMLA
----------------
sdesmalen-arm wrote:

nit:
```suggestion
  SDValue Constant = N->getOpcode() == ISD::PARTIAL_REDUCE_FMLA
```

https://github.com/llvm/llvm-project/pull/159776