psci: Use bool in internal interfaces

Change-Id: I77c9cd2d1d6d0122cc49917fa686014bee154589
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/lib/psci/psci_main.c b/lib/psci/psci_main.c
index 6a35ff6..fd822bc 100644
--- a/lib/psci/psci_main.c
+++ b/lib/psci/psci_main.c
@@ -82,7 +82,7 @@
 	}
 
 	/* Fast path for CPU standby.*/
-	if (is_cpu_standby_req(is_power_down_state, target_pwrlvl) != 0) {
+	if (is_cpu_standby_req(is_power_down_state, target_pwrlvl)) {
 		if  (psci_plat_pm_ops->cpu_standby == NULL)
 			return PSCI_E_INVALID_PARAMS;