CVE-2025-21767 clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context

In the Linux kernel, the following vulnerability has been resolved: clocksource: Use migratedisable to avoid calling getrandomu32 in atomic context The following bug report happened with a PREEMPTRT kernel: BUG: sleeping function called from invalid context at kernel/locking/spinlockrt.c:48...