Fix a bug in mkldnn emitter. (#2878)

src/ngraph/runtime/cpu/mkldnn_emitter.cpp

@@ -853,8 +853,8 @@ void MKLDNNEmitter::build_max_pooling_backward(std::vector<mkldnn::primitive*>&
 
     mkldnn::pooling_forward::primitive_desc fwd_pd{fwd_pool_desc, executor::global_cpu_engine};
 
-    size_t ws_index = m_primitive_deps[fwd_pool_index][2];
-    build_memory_primitive(fwd_pd.workspace_primitive_desc().desc(), ws_index);
+    size_t ws_index = fdeps[2];
+    build_memory_primitive(mkldnn_primitives, fwd_pd.workspace_primitive_desc().desc(), ws_index);
     bdeps[1] = ws_index;
 
     // Allocate workspace