TF-flavoured group convolution (#1182)

* tf group convolution

* change perms

src/ngraph/runtime/cpu/pass/cpu_mat_fusion.cpp

@@ -254,6 +254,8 @@ std::shared_ptr<Node> fuse_group_convolution(const std::shared_ptr<Node>& n)
     auto concat = std::dynamic_pointer_cast<op::Concat>(n);
     std::shared_ptr<op::Convolution> sconv;
 
+    NodeVector slices;
+
     const size_t CHANNEL = 1;
     if (concat->get_concatenation_axis() != CHANNEL)
     {
@@ -296,9 +298,15 @@ std::shared_ptr<Node> fuse_group_convolution(const std::shared_ptr<Node>& n)
         auto slice = pattern_map[slice_weights_label];
         if (weights->get_shape().at(IC) != slice->get_shape().at(IC))
         {
-            NGRAPH_DEBUG << "slices are done on the wrong axis (IC)";
-            return {nullptr};
+            slices.push_back(slice);
+        }
     }
+
+    //TF-flavoured group convolution needs channels re-arranged
+    const size_t CONCAT_AXIS_OC = 0;
+    if (!slices.empty())
+    {
+        weights = std::make_shared<op::Concat>(slices, CONCAT_AXIS_OC);
     }
 
     auto new_conv = std::make_shared<op::GroupConvolution>(data,