tlv: avoid misaligned memory access

They cause unit test crashing on ARM platform.

refs: #4609

Change-Id: Ifdb0401529de48b5c08ebcf6938d80ba87ff883d
diff --git a/tests/tlv/test-routing-table.cpp b/tests/tlv/test-routing-table.cpp
index c7af5ae..85a9850 100644
--- a/tests/tlv/test-routing-table.cpp
+++ b/tests/tlv/test-routing-table.cpp
@@ -32,13 +32,14 @@
 const uint8_t RoutingTableData1[] =
 {
   // Header
-  0x90, 0x22,
+  0x90, 0x24,
   // Routing table entry
-  0x91, 0x20,
+  0x91, 0x22,
     // Destination
     0x8e, 0x09, 0x07, 0x07, 0x08, 0x05, 0x64, 0x65, 0x73, 0x74, 0x31,
     // Nexthop
-    0x8f, 0x13, 0x8d, 0x07, 0x6e, 0x65, 0x78, 0x74, 0x68, 0x6f, 0x70, 0x86, 0x08, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0xfa, 0x3f
+    0x8f, 0x15, 0x8d, 0x07, 0x6e, 0x65, 0x78, 0x74, 0x68, 0x6f, 0x70,
+    0x86, 0x0a, 0x86, 0x08, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0xfa, 0x3f
 };
 
 const uint8_t RoutingTableData2[] =