Impact: avoid spurious lapic timer events on shutdown

The apic timer might be close to firing when it is shutdown. We can
not really disable the timer - we just mask the interrupt. That way we
can get an extra interrupt when it is reenabled. Set the counter to
max on shutdown to avoid this.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>