CVE-2025-40260 sched_ext: Fix scx_enable() crash on helper kthread creation failure

In the Linux kernel, the following vulnerability has been resolved: schedext: Fix scxenable crash on helper kthread creation failure A crash was observed when the schedext selftests runner was terminated with Ctrl+\ while test 15 was running: NIP c00000000028fa58 scxenable.constprop.0+0x358/0x12b...