!9590 s390/ap: Fix crash in AP internal function modify_bitmap()

Merge Pull Request from: @ci-robot 
 
PR sync from: liwei <liwei728@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/67GY33V43LYXBQBNTOKYW64VRWU4LBUX/ 
 
https://gitee.com/src-openeuler/kernel/issues/IA8AEM 
 
Link:https://gitee.com/openeuler/kernel/pulls/9590

 

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