cpuidle: powernv: Don't continually set thread priority in snooze_loop()

The powerpc64 kernel exception handlers have preserved thread priorities
for a long time now, so there is no need to continually set it.

Just set it once on entry and once exit.

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

@@ -56,8 +56,8 @@ static int snooze_loop(struct cpuidle_device *dev,
 
 	snooze_exit_time = get_tb() + snooze_timeout;
 	ppc64_runlatch_off();
+	HMT_very_low();
 	while (!need_resched()) {
-		HMT_very_low();
 		if (snooze_timeout_en && get_tb() > snooze_exit_time)
 			break;
 	}