cpuidle: powernv: Avoid a branch in the core snooze_loop() loop

When in the snooze_loop() we want to take up the least amount of
resources. On my version of gcc (6.3), we end up with an extra
branch because it predicts snooze_timeout_en to be false, whereas it
is almost always true.

Use likely() to avoid the branch and be a little nicer to the
other non idle threads on the core.
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

@@ -58,7 +58,7 @@ static int snooze_loop(struct cpuidle_device *dev,
 	ppc64_runlatch_off();
 	HMT_very_low();
 	while (!need_resched()) {
-		if (snooze_timeout_en && get_tb() > snooze_exit_time)
+		if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time)
 			break;
 	}