Replace hardcoded values in ndn-cxx by MAX_NDN_PACKET_SIZE

Change-Id: I0e116cd2a39781f0d56e156ac517ecadd49b8741
Refs: #3407
diff --git a/src/encoding/encoder.cpp b/src/encoding/encoder.cpp
index 4b32c10..3c15943 100644
--- a/src/encoding/encoder.cpp
+++ b/src/encoding/encoder.cpp
@@ -24,7 +24,7 @@
 namespace ndn {
 namespace encoding {
 
-Encoder::Encoder(size_t totalReserve/* = 8800*/, size_t reserveFromBack/* = 400*/)
+Encoder::Encoder(size_t totalReserve/* = MAX_NDN_PACKET_SIZE*/, size_t reserveFromBack/* = 400*/)
   : m_buffer(new Buffer(totalReserve))
 {
   m_begin = m_end = m_buffer->end() - (reserveFromBack < totalReserve ? reserveFromBack : 0);