ubifs: Fix some kernel-doc comments

Remove warnings found by running scripts/kernel-doc,
which is caused by using 'make W=1'.
fs/ubifs/journal.c:1221: warning: Function parameter or member
'old_inode' not described in 'ubifs_jnl_rename'
fs/ubifs/journal.c:1221: warning: Function parameter or member 'old_nm'
not described in 'ubifs_jnl_rename'
fs/ubifs/journal.c:1221: warning: Function parameter or member
'new_inode' not described in 'ubifs_jnl_rename'
fs/ubifs/journal.c:1221: warning: Function parameter or member 'new_nm'
not described in 'ubifs_jnl_rename'
fs/ubifs/journal.c:1221: warning: Function parameter or member
'whiteout' not described in 'ubifs_jnl_rename'
fs/ubifs/journal.c:1221: warning: Excess function parameter 'old_dentry'
description in 'ubifs_jnl_rename'
fs/ubifs/journal.c:1221: warning: Excess function parameter 'new_dentry'
description in 'ubifs_jnl_rename'

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>