core: use FaceUri from ndn-cxx

refs #2143

Change-Id: Ida06daf406f941a699c9f1013450951db3cd28e9
diff --git a/core/network-interface.hpp b/core/network-interface.hpp
index baaa85b..c5296a1 100644
--- a/core/network-interface.hpp
+++ b/core/network-interface.hpp
@@ -30,8 +30,14 @@
 
 #include <net/if.h>
 
+#include <ndn-cxx/util/ethernet.hpp>
+
 namespace nfd {
 
+namespace ethernet = ndn::util::ethernet;
+
+/** \brief contains information about a network interface
+ */
 class NetworkInterfaceInfo
 {
 public: