CVE-2026-43132 dm-verity: correctly handle dm_bufio_client_create() failure

In the Linux kernel, the following vulnerability has been resolved: dm-verity: correctly handle dmbufioclientcreate failure If either of the calls to dmbufioclientcreate in verityfecctr fails, then dmbufioclientdestroy is later called with an ERRPTR argument. That causes a crash. Fix this...