[ONNX] Mapping reduction string from onnx add to torch sum

Author: AmosLewis

lib/Conversion/TorchOnnxToTorch/DefaultDomainQtoZ.cpp

@@ -635,10 +635,12 @@ void mlir::torch::onnx_c::populateDefaultDomainQtoZ(
 
         // TODO: Implement max and min cases
         if (reduction == "mul") {
-          reduction = "multiply";
+          reduction = "prod";
         } else if (reduction == "max" || reduction == "min") {
           return rewriter.notifyMatchFailure(
               binder.op, "max/min reduction unsupported for scatter elements");
+        } else if (reduction == "add") {
+          reduction = "sum";
         }
 
         Value cstStrReduction =