Update api-ref for port group create

Update the facts that name and MAC address is not mandatory when
creating port groups.

Change-Id: I214cdab5789923341cdb2100b425958df6053d68

api-ref/source/baremetal-api-v1-portgroups.inc

@@ -83,6 +83,7 @@ Request
 
     - node_uuid: node_uuid
     - address: portgroup_address
+    - name: portgroup_name
 
 **Example Portgroup creation request:**
 

api-ref/source/parameters.yaml

@@ -829,7 +829,7 @@ portgroup_address:
     Physical hardware address of this Portgroup, typically the hardware
     MAC address.
   in: body
-  required: true
+  required: false
   type: string
 portgroup_internal_info:
   description: |