Reducing duplicated values on values files for SiaB

Reduced the amount of duplicated values between seba-ponsim values file.
To deploy, for example, the latest of seba-ponsim, now both seba-ponsim.yaml and seba-pomsim-latest.yaml values files need to be used with the specified order.
Makefile for SiaB is modified accordingly in the patch https://gerrit.opencord.org/#/c/16743/.
Also:
- removed stratumEnabled value from Mininet chart and added mnStratumSwitchCount
- moved bngAppUrl and bngAppVersion values on root of values file

Change-Id: I26b8e91f868646adc06f2c1feea72b333defd487
diff --git a/configs/seba-ponsim-stratum.yaml b/configs/seba-ponsim-stratum.yaml
index 171a582..08d38e4 100644
--- a/configs/seba-ponsim-stratum.yaml
+++ b/configs/seba-ponsim-stratum.yaml
@@ -14,50 +14,22 @@
 # limitations under the License.
 
 # Values file for deploying SEBA with Ponsim and Stratum
-# Use this file to deploy the service versions specified in the Helm charts.
+# Use this file together with seba-ponsim.yaml to deploy the service versions
+# specified in the Helm charts.
+
+# ----------- Values modified or added wrt seba-ponsim.yaml --------------------
 
 images:
-  # Mininet image
   mininet:
     repository: 'opencord/mn-stratum-siab'
     tag: 'master'
-    pullPolicy: Always
 
-# voltha
-etcd-cluster:
-  clusterSize: 1
-
-# in workflow/att-workflow service chart
-att-workflow-driver:
-  # this is mandatory, it's needed to correctly configure the kafka endpoint
-  kafkaService: cord-kafka
-
-# in workflow/tt-workflow service chart
-tt-workflow-driver:
-  image:
-    repository: andybavier/test-image-synchronizer
-    tag: tt-workflow-driver
-
-  # this is mandatory, it's needed to correctly configure the kafka endpoint
-  kafkaService: cord-kafka
-
-# in mininet chart
+# In mininet chart
 # FIXME: check if multicast is working
 enableMulticast: false
 topoScript: '/toposcripts/topo_stratum.py'
-stratumEnabled: true
+mnStratumSwitchCount: 1
 
-# in ponsim-pod chart
-bandwidthProfiles: true
-legacyPonsim: false
-
-# fabric
 fabric:
-  enabled: true
   stratum:
-    driverAppId: 'org.onosproject.drivers.bmv2'
-    # Enable stratum
     enabled: true
-    # Use BMv2 pipeconf (already in ONOS)
-    pipeconfAppExternal: false
-    pipeconfAppId: 'org.onosproject.pipelines.fabric'