Print device time

src/targets/gpu/driver/compile_op.cpp

@@ -39,7 +39,10 @@ struct compile_op : action<compile_op>
         auto inputs = p.parse_shapes(v.at("inputs"));
         auto op     = gpu::compile_op(v.at("name").to<std::string>(), ctx, inputs, v);
         auto [host_time, device_time] = time_op(ctx, op, inputs, p.get(v, "iterations", 100));
-        std::cout << op << ": " << host_time << "ms" << std::endl;
+        std::cout << op << ": " << host_time << "ms";
+        if (device_time > 0)
+            std::cout << ", " << device_time << "ms";
+        std::cout << std::endl;
     }
 };