ubifs-utils: libubifs: Support some file operations

ubifs-utils: libubifs: Support some file operations

Add some file operations, such as ubifs_lookup, ubifs_mkdir, etc., this
is a preparation for recovering disconnected files or root dir in fsck.
File writing operations are based on the journal subsystem, generated
dirty data depends on a new commit in subsequent steps to update disk
content.

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