Name unnamed namespace as convolution_details.

ngraph/core/reference/include/ngraph/runtime/reference/convolution.hpp

@@ -38,7 +38,7 @@ namespace ngraph
     {
         namespace reference
         {
-            namespace
+            namespace convolution_details
             {
                 constexpr size_t in_batch_axis = 0;
                 constexpr size_t in_channel_axis = 1;
@@ -191,6 +191,8 @@ namespace ngraph
                              const Strides&)
 
             {
+                using namespace convolution_details;
+
                 // this implementation supports 1D, 2D and 3D convolutions
                 NGRAPH_CHECK(in_shape.size() >= 3 && in_shape.size() <= 5,
                              "Unsupported input rank: ",