CVE-2026-64185: sysfs: don't remove existing directory on update failure

In the Linux kernel, the following vulnerability has been resolved:

sysfs: don't remove existing directory on update failure

When sysfsupdategroup() is called for a named group and createfiles() fails (e.g. -ENOMEM), internalcreategroup() calls kernfsremove(kn) on the group directory. In the update path, kn was obtained via kernfsfindandget() and refers to a directory that already existed before this call. Removing it silently destroys a sysfs group that the caller did not create.

Only remove the directory if we created it ourselves. On update failure the directory remains as it is left empty by removefiles() inside createfiles(), but can be repopulated by a retry.