FROMGIT: f2fs: allow to read node block after shutdown

If block address is still alive, we should give a valid node block even after
shutdown. Otherwise, we can see zero data when reading out a file.

Bug: 257271565
Cc: stable@vger.kernel.org
Fixes: 83a3bfdb ("f2fs: indicate shutdown f2fs to allow unmount successfully")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 6953bf65286d git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git dev)
Change-Id: Ifb70f6c73bd67d5112ee9fa1a5e4ad8e10ae8517