!6820 s390/dasd: fix Oops in dasd_alias_get_start_dev due to missing pavgroup

Merge Pull Request from: @ci-robot 
 
PR sync from: Li Zetao <lizetao1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/JS4ZFFQINHFCOQ4SOLT2UL6PPPBZSTUS/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9KHGT 
 
Link:https://gitee.com/openeuler/kernel/pulls/6820

 

Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Reviewed-by: Zhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>