fix conv parser of onnx

mindspore/lite/tools/converter/parser/onnx/onnx_conv_parser.cc

@@ -21,6 +21,7 @@
 
 namespace mindspore {
 namespace lite {
+constexpr int32_t kSingleGrounp = 1;
 bool OnnxConvParser::ParseGroupConvolution(const std::unique_ptr<schema::Conv2DT> &attr, schema::CNodeT *op) {
   MS_LOG(DEBUG) << "onnx DepthwiseConvParser";
   if (attr == nullptr || attr->group != attr->channelIn) {
@@ -171,7 +172,7 @@ STATUS OnnxConvParser::Parse(const onnx::GraphProto &onnx_graph, const onnx::Nod
     attr->activationType = schema::ActivationType_NO_ACTIVATION;
   }
 
-  if (attr->group == attr->channelOut) {
+  if (attr->group > kSingleGrounp) {
     if (!ParseGroupConvolution(attr, op)) {
       MS_LOG(ERROR) << "Convert Convolution to Depthwise failed";
       return RET_ERROR;