fix undefined issue when with_gpu

paddle/operators/math/math_function.cc

@@ -277,6 +277,14 @@ void set_constant_with_place<platform::CPUPlace>(
                            TensorSetConstantCPU(tensor, value));
 }
 
+template <>
+void set_constant_with_place<platform::MKLDNNPlace>(
+    const platform::DeviceContext& context, framework::Tensor* tensor,
+    float value) {
+  framework::VisitDataType(framework::ToDataType(tensor->type()),
+                           TensorSetConstantCPU(tensor, value));
+}
+
 struct TensorSetConstantWithPlace : public boost::static_visitor<void> {
   TensorSetConstantWithPlace(const platform::DeviceContext& context,
                              framework::Tensor* tensor, float value)

paddle/platform/place.h

@@ -31,7 +31,7 @@ struct CPUPlace {
   inline bool operator!=(const CPUPlace &) const { return false; }
 };
 
-struct MKLDNNPlace : public CPUPlace {
+struct MKLDNNPlace {
   MKLDNNPlace() {}
 
   // needed for variant equality comparison