add batch size to the mkldnn matmul cache key (#24408)

test=develop

paddle/fluid/operators/mkldnn/matmul_mkldnn_op.cc

@@ -322,9 +322,10 @@ static std::shared_ptr<MatMulFactory<XT, YT, OT>> GetPrimitiveFactory(
     const ExecutionContext& ctx) {
   const auto& out_name = ctx.OutputName("Out");
   const auto& dev_ctx = ctx.template device_context<MKLDNNDeviceContext>();
+  const auto batch_size = ctx.Input<Tensor>("X")->dims()[0];
 
   const std::string key =
-      platform::CreateKey(platform::ThreadIDasStr(), out_name);
+      platform::CreateKey(platform::ThreadIDasStr(), batch_size, out_name);
 
   auto factory =
       std::static_pointer_cast<MatMulFactory<XT, YT, OT>>(dev_ctx.GetBlob(key));