[Bug fix] Do not quantize weights Y when matmul X and Y both other ops outputs (#43297)

* fix some matmul that X and Y both other ops outputs, do not dequantize the Y.

* fix CI format

* fix according to review

paddle/fluid/framework/ir/mkldnn/quant_dequant_mkldnn_pass.cc

@@ -353,10 +353,9 @@ bool QuantDequantMkldnnPass::IsInt8Weight(
   auto* op_desc = op_node->Op();
   auto var_name = op_desc->Input(weight_name)[0];
   auto* var = scope->FindVar(var_name);
-  PADDLE_ENFORCE_NOT_NULL(
-      var, platform::errors::NotFound(
-               "The input persistable [%s] var of [%s] op is not found.",
-               var_name, op_desc->Type()));
+  if (var == nullptr) {
+    return false;
+  }
   auto* weight_tensor = var->GetMutable<LoDTensor>();
   auto* weight_data = weight_tensor->data<float>();
   bool is_int8 = true;