am d2f07839: Merge topic \'f2fs\'

* commit 'd2f07839cb85ad5b78665892deb12d2d353daab0':
  f2fs utils: Add mkf2fsuserimg.sh and make_f2fs
  f2fs_utils: support new f2fs-tools f2fs_finalize_device API.
  f2fs_utils: provide sparse io and dynamic load.