ACPI: Idle C-states disabled by max_cstate should not disable the TSC

Processor idle power states C2 and C3 stop the TSC on many machines.
Linux recognizes this situation and marks the TSC as unstable:

Marking TSC unstable due to TSC halts in idle

But if those same machines are booted with "processor.max_cstate=1",
then there is no need to validate C2 and C3, and no need to
disable the TSC, which can be reliably used as a clocksource.
Signed-off-by: NLen Brown <len.brown@intel.com>
Acked-by: NThomas Gleixner <tglx@linutronix.de>

drivers/acpi/processor_idle.c

@@ -582,7 +582,7 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
 
 	pr->power.timer_broadcast_on_state = INT_MAX;
 
-	for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
+	for (i = 1; i < ACPI_PROCESSOR_MAX_POWER && i <= max_cstate; i++) {
 		struct acpi_processor_cx *cx = &pr->power.states[i];
 
 		switch (cx->type) {