Pull UBIFS updates from Richard Weinberger:

 - Support for zstd compression

 - Support for offline signed filesystems

 - Various fixes for regressions

* tag 'upstream-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs:
  ubifs: Don't leak orphans on memory during commit
  ubifs: Check link count of inodes when killing orphans.
  ubifs: Add support for zstd compression.
  ubifs: support offline signed images
  ubifs: remove unnecessary check in ubifs_log_start_commit
  ubifs: Fix typo of output in get_cs_sqnum
  ubifs: Simplify redundant code
  ubifs: Correctly use tnc_next() in search_dh_cookie()