Added support for running SiaB with SD-BNG

- new mininet topology with PPPoE server
- new fabric configuration for Ponsim
- new DT-workflow
- new values file to run SD-BNG on SiaB

Change-Id: Ib9d61111d6399e9240afb60bb6a77f152a6ecd01
diff --git a/xos-profiles/ponsim-pod/values.yaml b/xos-profiles/ponsim-pod/values.yaml
index 01a7d70..6a992b0 100644
--- a/xos-profiles/ponsim-pod/values.yaml
+++ b/xos-profiles/ponsim-pod/values.yaml
@@ -59,3 +59,8 @@
 fabric:
   stratum:
     enabled: false
+bng:
+  external:
+    enabled: true
+  embedded:
+    enabled: false