timekeeping: Add the boot clock to system time snapshot

timekeeping: Add the boot clock to system time snapshot

For tracing purpose, the boot clock is interesting as it doesn't stop on
suspend. Export it as part of the time snapshot. This will later allow
the hypervisor to add boot clock timestamps to its events.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20240911093029.3279154-5-vdonnefort@google.com