Some more debugging

Print command return code after invoking 'Read part ID' command.

lpc.c

@@ -100,6 +100,7 @@ int lpc_read_partid(struct lpc_device *dev) {
   int res;
   int partid;
   res = lpc_command("J\r\n");
+  sprog_error("Command return code is %d\n", res);
   if(res!=0)
     return res;
   if(scanf("%d\r\n", &partid)<1)