Gate sub-components section on eligible devices via can_have_subcomponents()

templates/device_detail.html

@@ -108,7 +108,7 @@
   </table>
 </div>
 
-{% if device.children or not device.is_subcomponent() %}
+{% if device.children or device.can_have_subcomponents() %}
 <div class="card">
   {% if device.children %}
   <h2>Sub-components</h2>