ubifs-utils: Adapt tnc subsystem in libubifs

ubifs-utils: Adapt tnc subsystem in libubifs

Adapt tnc subsystem(tnc.c,tnc_misc.c,tnc_commit.c) in libubifs, compared
with linux kernel implementations:
 1. Remove debug related functions(eg. dbg_check_inode_size), debug
    functions are not needed by fsck, because fsck will check fs in
    another way.
 2. Remove some functions(eg. ubifs_tnc_bulk_read) which won't be used
    in fsck/mkfs.
 3. Adapt tnc_delete and ubifs_search_zbranch to handle empty TNC case,
    which could happen in fsck.
 4. Don't skip checking the length of non-leaf index node's branch in
    read_znode.
 5. Adapt try_read_node to ignore %-EBADMSG, subsequent steps will check
    nodes carefully.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>