ensure USB config numbers always start from 1

Depending on which features (and thus USB configurations) are included
in the firmware, we need to re-define the ordering of the configuration
numbers, as the Atmel USBD driver simply assumes that configurations are
numbered 1..N without any gaps in the sequence.

firmware/src_simtrace/usb.c

@@ -32,6 +32,7 @@
  *----------------------------------------------------------------------------*/
 
 #include "board.h"
+#include "simtrace.h"
 #include "utils.h"
 
 #include <cciddriverdescriptors.h>