ubifs: Fix unattached inode when powercut happens in creating

For selinux or encryption scenarios, UBIFS could become inconsistent
while creating new files in powercut case. Encryption/selinux related
xattrs will be created before creating file dentry, which makes creation
process is not atomic, details are shown as:

Encryption case:
ubifs_create
 ubifs_new_inode
  fscrypt_set_context
   ubifs_xattr_set
    create_xattr
     ubifs_jnl_update  // Disk: xentry xinode inode(LAST_OF_NODE_GROUP)
 >> power cut <<
 ubifs_jnl_update  // Disk: dentry inode parent_inode(LAST_OF_NODE_GROUP)

Selinux case:
ubifs_create
 ubifs_new_inode
 ubifs_init_security
  security_inode_init_security
   ubifs_xattr_set
    create_xattr
     ubifs_jnl_update  // Disk: xentry xinode inode(LAST_OF_NODE_GROUP)
 >> power cut <<
 ubifs_jnl_update  // Disk: dentry inode parent_inode(LAST_OF_NODE_GROUP)

Above process will make chk_fs failed in next mounting:
 UBIFS error (ubi0:0 pid 7995): dbg_check_filesystem [ubifs]: inode 66
 nlink is 1, but calculated nlink is 0

Fix it by allocating orphan inode for each non-xattr file creation, then
removing orphan list in journal writing process, which ensures that both
xattr and dentry be effective in atomic when powercut happens.

Fixes: d7f0b70d ("UBIFS: Add security.* XATTR support for the UBIFS")
Fixes: d475a507 ("ubifs: Add skeleton for fscrypto")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218309


Suggested-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>