!7786 powerpc/powernv: Add a null pointer check in opal_event_init()

Merge Pull Request from: @ci-robot 
 
PR sync from: Guo Mengqi <guomengqi3@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/5DK54VIPFVCP3VE2RWGWH3IRP44B5QXT/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9Q9IH 
 
Link:https://gitee.com/openeuler/kernel/pulls/7786

 

Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>