ubifs-utils: Adapt ubifs header file in libubifs

ubifs-utils: Adapt ubifs header file in libubifs

Adapt ubifs header file in libubifs, compared with linux kernel
implementations:
 1. New header file contains all definitions in common/ubifs.h
 2. Remove some structures(eg. ubifs_mount_opts, bu_info) and
    functions(eg. ubifs_sync_wbufs_by_inode, ubifs_jnl_XXX) which
    won't be used in fsck/mkfs.
 3. Modify some authentication related functions, keep functions
    that mkfs may need, other functions are defined as empty.
 4. Move ubifs message printing functions(ubifs_err/warn/msg) which
    are originally defined in misc.c into ubifs.h.

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