CVE-2026-68416 mtd: fix double free and WARN_ON in add_mtd_device() error paths

In the Linux kernel, the following vulnerability has been resolved: mtd: fix double free and WARNON in addmtddevice error paths When deviceregister or mtdnvmemadd fails inside addmtddevice for a partition, the error handling triggers mtdrelease via putdevice or deviceunregister. mtdrelease calls...