Fixed Gemm support

hpvm/projects/onnx/frontend/graph_builder.py

@@ -116,6 +116,7 @@ class DFG(object):
             "MaxPool": g.MaxPool2DNode,
             "AveragePool": g.AveragePool2DNode,
             "MatMul": g.MatMulNode,
+            "Gemm": g.MatMulNode,
             "Add": g.AddNode,
             "Softmax": g.SoftMaxNode,
             "Relu": g.ReluNode,