[Yaffs] yaff2 scan error info

NAND FLASH will
be scanned whening yaffs2 mount.If not find checkpoint,yaffs2 will begin check
chunk.But if get error information from NAND FLASH,yaffs2 may be run this
code：
in = yaffs_retype_obj(in, oh ? oh->type : tags.extra_obj_type);

If in->variant_type ==YAFFS_OBJECT_TYPE_DIRECTORY ,It just put object's
childrens in lost+found,but not deal with siblings list.It is need deal with
siblings list?