!22409 Set "dst_type" attribute when creating Cast op

Merge pull request !22409 from DeshiChen/0826_cast_dst_type

mindspore/ccsrc/backend/optimizer/gpu/reduce_precision_fusion.cc

@@ -36,6 +36,7 @@ void ReducePrecision(const FuncGraphPtr &graph, const AnfNodePtr &node, size_t i
   std::vector<AnfNodePtr> inputs = {NewValueNode(prim), AnfAlgo::GetInputNode(utils::cast<CNodePtr>(node), i)};
   auto cast = graph->NewCNode(inputs);
   MS_EXCEPTION_IF_NULL(cast);
+  prim->AddAttr("dst_type", TypeIdToType(cast_type));
   auto cast_shape = {AnfAlgo::GetInputDeviceShape(node, i)};
   AnfAlgo::SetOutputInferTypeAndShape({cast_type}, cast_shape, cast.get());
   FuncGraphManagerPtr manager = graph->manager();