Don't pass unused args to printf

The final print does not print any content, only the byte-offset of the
end-block, which makes the A, B params unused. From gcc:

    bd.c:77:17: warning: too many arguments for format [-Wformat-extra-args]
        if (o) printf("%08x\n", o, A, B);

tool/viz/bd.c

@@ -77,6 +77,6 @@ int main(int argc, char *argv[]) {
     }
     o += n;
   }
-  if (o) printf("%08x\n", o, A, B);
+  if (o) printf("%08x\n", o);
   return !feof(f);
 }