data+name: don't uselessly increment totalLength in wireEncode

The variable was never used after being incremented.

Change-Id: Icdc16959004d9496ab06a43634eaceee798878d6
diff --git a/src/name-component.cpp b/src/name-component.cpp
index e02ee7e..1cd0d16 100644
--- a/src/name-component.cpp
+++ b/src/name-component.cpp
@@ -431,8 +431,8 @@
     totalLength += encoder.appendByte(0);
   }
 
-  totalLength += encoder.prependVarNumber(totalLength);
-  totalLength += encoder.prependVarNumber(type());
+  encoder.prependVarNumber(totalLength);
+  encoder.prependVarNumber(type());
 
   return encoder.block();
 }