ksmbd: smbd: fix dma mapping error in smb_direct_post_send_data

mainline inclusion
from mainline-5.15-rc1
commit 72d6cbb5
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I60T7G
CVE: NA

Reference: https://git.kernel.org/torvalds/linux/c/72d6cbb533d4



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

Becase smb direct header is mapped and msg->num_sge
already is incremented, the decrement should be
removed from the condition.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-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>