ubifs-utils: Adapt orphan.c in libubifs

ubifs-utils: Adapt orphan.c in libubifs

Adapt orphan.c in libubifs, compared with linux kernel implementations:
 1. Keep the commit related implementations, because do_commit depends
    on these functions which will be invoked in fsck.
 2. Keep the orphan replaying implementations, because fsck needs them.
 3. Other implementations are removed which won't be used in mkfs/fsck.

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