It is better to return a linux error code than define a private constant.

Link: https://lore.kernel.org/r/1572952082-6681-9-git-send-email-liweihang@hisilicon.comSigned-off-by: NYixian Liu <liuyixian@huawei.com>
Signed-off-by: NWenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: NWeihang Li <liweihang@hisilicon.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>