Enable RDC link Status feature

1.add link status APIs
   2.Add link status example for link status API usage

rdci/include/RdciTopologyLinkSubSystem.h

@@ -34,7 +34,7 @@ class RdciTopologyLinkSubSystem : public RdciSubSystem {
  private:
   void show_help() const;
   enum OPERATIONS {
-    POLICY_UNKNOWN = 0,
+    TOPOLOGY_UNKNOWN = 0,
     TOPOLOGY_INDEX,
   } topology_ops_;
   uint32_t group_index_;