ksmbd: Delete an invalid argument description in smb2_populate_readdir_entry()

A warning is reported because an invalid argument description, it is found
by running scripts/kernel-doc, which is caused by using 'make W=1'.
fs/ksmbd/smb2pdu.c:3406: warning: Excess function parameter 'user_ns'
description in 'smb2_populate_readdir_entry'

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Fixes: 475d6f98

 ("ksmbd: fix translation in smb2_populate_readdir_entry()")
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Steve French <stfrench@microsoft.com>