!9512 drm: vc4: Fix possible null pointer dereference

Merge Pull Request from: @ci-robot 
 
PR sync from: Ze Zuo <zuoze1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/LTF2TQKOPW2ZNGHFZI4PBA2KCOPO7QI4/ 
 
https://gitee.com/src-openeuler/kernel/issues/IA6SGI 
 
Link:https://gitee.com/openeuler/kernel/pulls/9512

 

Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>