ubi: Fix rollback for explicit UBI device numbers

In the Linux kernel, the following vulnerability has been resolved: ubi: Fix rollback for explicit UBI device numbers ubi_init_attach() rolls back module initialization failures by scanning ubi_devices[0..i-1], where i is the mtd= parameter index. That assumes the parameter index matches the UBI device number. That assumption is not true when mtd= specifies an explicit ubi_num. A successfully attached device can be stored at a higher ubi_devices[] slot, and a later failure can miss it during rollback. Scan the full ubi_devices[] array and detach by the actual array index, matching the way UBI devices are stored.