make_dev_ssd: fix the offset for enable_rw_mount

scripts/image_signing/make_dev_ssd.sh

 #!/bin/sh
 #
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # This script can change key (usually developer keys) and kernel config
 # of a kernels on SSD.
 
 SCRIPT_BASE="$(dirname "$0")"
@@ skipping 207 matching lines @@
   ensure_files_exist \
     "$KERNEL_KEYBLOCK" \
     "$KERNEL_DATAKEY" \
     "$KERNEL_PUBKEY" \
     "$FLAGS_image" ||
     exit 1
 
   # Make the root filesystem remountable if needed.
   if [ ${FLAGS_remove_rootfs_verification} = $FLAGS_TRUE ]; then
     local root_offset=$(partoffset "$FLAGS_image" 3)
-    enable_rw_mount "$FLAGS_image" "$root_offset"
+    enable_rw_mount "$FLAGS_image" "$((root_offset * 512))"
   fi
 
   resign_ssd_kernel "$FLAGS_image" || num_signed=$?
 
   debug_msg "Complete."
   if [ $num_signed -gt 0 -a $num_signed -le 2 ]; then
     # signed 1 or two kernels
     echo "Successfully re-signed $num_signed kernel(s) on device $FLAGS_image".
   else
     err_die "Failed re-signing kernels."
   fi
 }
 
 main