Fix build of dtm.cc on RISC-V targets

We don't actually need encoding.h, so don't include it.

fesvr/dtm.cc

@@ -1,6 +1,5 @@
 #include "dtm.h"
 #include "debug_defines.h"
-#include "encoding.h"
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>