encoding: remove duplicate buf() and get() methods from Buffer class

Change-Id: If885d4199d6c9df9b9b46664c3641c9a14a77eab
diff --git a/tools/ndnsec/cert-gen.cpp b/tools/ndnsec/cert-gen.cpp
index f63a2ea..dbab9cb 100644
--- a/tools/ndnsec/cert-gen.cpp
+++ b/tools/ndnsec/cert-gen.cpp
@@ -136,7 +136,7 @@
   try {
     Buffer keyContent = certRequest.getPublicKey();
     t::PublicKey pubKey;
-    pubKey.loadPkcs8(keyContent.buf(), keyContent.size());
+    pubKey.loadPkcs8(keyContent.data(), keyContent.size());
   }
   catch (const std::exception& e) {
     std::cerr << "ERROR: " << e.what() << std::endl;