cpuidle: powernv: Don't bounce between low and very low thread priority

The core of snooze_loop() continually bounces between low and very
low thread priority. Changing thread priorities is an expensive
operation that can negatively impact other threads on a core.

All CPUs that can run PowerNV support very low priority, so we can
avoid the change completely.
Signed-off-by: Anton Blanchard <anton@samba.org>
Reviewed-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/cpuidle-powernv.c

@@ -57,7 +57,6 @@ static int snooze_loop(struct cpuidle_device *dev,
 	snooze_exit_time = get_tb() + snooze_timeout;
 	ppc64_runlatch_off();
 	while (!need_resched()) {
-		HMT_low();
 		HMT_very_low();
 		if (snooze_timeout_en && get_tb() > snooze_exit_time)
 			break;