!3944 time: Handle negative seconds correctly in timespec64_to_ns()

Merge Pull Request from: @ci-robot 
 
PR sync from: liwei <liwei728@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/FR4XUV6WTHZNRR6J73NOGL2BCXJOHN6B/ 
 
https://gitee.com/openeuler/kernel/issues/I8MCB5 
 
Link:https://gitee.com/openeuler/kernel/pulls/3944

 

Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Reviewed-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>