refactor(psci): extract cm_prepare_el3_exit_ns() to a common location

PSCI on and suspend wakeup both end with a cm_prepare_el3_exit_ns() call.
Since they are equivalent to the caller, move the call to just after the
*_finish calls to deduplicate it.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I05c16dc6613aba357d20cc39cc43aab803d675e0

lib/psci/psci_common.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2022, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -1036,6 +1036,13 @@ void psci_warmboot_entrypoint(void)
 	else
 		psci_cpu_suspend_finish(cpu_idx, &state_info);
 
+	/*
+	 * Generic management: Now we just need to retrieve the
+	 * information that we had stashed away during the cpu_on
+	 * call to set this cpu on its way.
+	 */
+	cm_prepare_el3_exit_ns();
+
 	/*
 	 * Set the requested and target state of this CPU and all the higher
 	 * power domains which are ancestors of this CPU to run.

lib/psci/psci_on.c

@@ -225,11 +225,4 @@ void psci_cpu_on_finish(unsigned int cpu_idx, const psci_power_state_t *state_in
 	/* Populate the mpidr field within the cpu node array */
 	/* This needs to be done only once */
 	psci_cpu_pd_nodes[cpu_idx].mpidr = read_mpidr() & MPIDR_AFFINITY_MASK;
-
-	/*
-	 * Generic management: Now we just need to retrieve the
-	 * information that we had stashed away during the cpu_on
-	 * call to set this cpu on its way.
-	 */
-	cm_prepare_el3_exit_ns();
 }

lib/psci/psci_suspend.c

@@ -367,11 +367,4 @@ void psci_cpu_suspend_finish(unsigned int cpu_idx, const psci_power_state_t *sta
 	psci_set_suspend_pwrlvl(PSCI_INVALID_PWR_LVL);
 
 	PUBLISH_EVENT(psci_suspend_pwrdown_finish);
-
-	/*
-	 * Generic management: Now we just need to retrieve the
-	 * information that we had stashed away during the suspend
-	 * call to set this cpu on its way.
-	 */
-	cm_prepare_el3_exit_ns();
 }