nvme-auth: remove the redundant req->cqe->result.u16 assignment operation

req->cqe->result.u16 has already been assigned in the previous line, no
need to do it again.

Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>