ksmbd: fix documentation for 2 functions

mainline inclusion
from mainline-5.15-rc4
commit 1018bf24
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I60T7G
CVE: NA

Reference: https://git.kernel.org/torvalds/linux/c/1018bf24550f



-------------------------------

ksmbd_kthread_fn() and create_socket() returns 0 or error code, and not
task_struct/ERR_PTR.

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>