vhost scsi: fix error return code in vhost_scsi_set_endpoint()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 25b98b64

 ("vhost scsi: alloc cmds per vq instead of session")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Link: https://lore.kernel.org/r/1607071411-33484-1-git-send-email-zhangchangzhong@huawei.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>