plat/arm: css: Convert CSS_SYSTEM_PWR_STATE from macro to inline function

This is to fix a number of Coverity Scan DEADCODE defects, CID numbers
listed below, as reported from
https://scan.coverity.com/projects/arm-software-arm-trusted-firmware

CID 267023
CID 267022
CID 267020

Change-Id: I2963a799b210149e84ccab5c5b9082267ddfe337
Signed-off-by: Nariman Poushin <nariman.poushin@linaro.org>
diff --git a/plat/arm/css/common/css_pm.c b/plat/arm/css/common/css_pm.c
index 3df5b78..986cb08 100644
--- a/plat/arm/css/common/css_pm.c
+++ b/plat/arm/css/common/css_pm.c
@@ -96,7 +96,7 @@
 void css_pwr_domain_on_finish(const psci_power_state_t *target_state)
 {
 	/* Assert that the system power domain need not be initialized */
-	assert(CSS_SYSTEM_PWR_STATE(target_state) == ARM_LOCAL_STATE_RUN);
+	assert(css_system_pwr_state(target_state) == ARM_LOCAL_STATE_RUN);
 
 	/* Program the gic per-cpu distributor or re-distributor interface */
 	plat_arm_gic_pcpu_init();
@@ -149,7 +149,7 @@
 	css_power_down_common(target_state);
 
 	/* Perform system domain state saving if issuing system suspend */
-	if (CSS_SYSTEM_PWR_STATE(target_state) == ARM_LOCAL_STATE_OFF) {
+	if (css_system_pwr_state(target_state) == ARM_LOCAL_STATE_OFF) {
 		arm_system_pwr_domain_save();
 
 		/* Power off the Redistributor after having saved its context */
@@ -174,7 +174,7 @@
 		return;
 
 	/* Perform system domain restore if woken up from system suspend */
-	if (CSS_SYSTEM_PWR_STATE(target_state) == ARM_LOCAL_STATE_OFF)
+	if (css_system_pwr_state(target_state) == ARM_LOCAL_STATE_OFF)
 		/*
 		 * At this point, the Distributor must be powered on to be ready
 		 * to have its state restored. The Redistributor will be powered