feat(psci): add support for OS-initiated mode

This patch adds a `psci_validate_state_coordination` function that is
called by `psci_cpu_suspend_start` in OS-initiated mode.

This function validates the request per sections 4.2.3.2, 5.4.5, and 6.3
of the PSCI spec (DEN0022D.b):
- The requested power states are consistent with the system's state
- The calling core is the last running core at the requested power level

This function differs from `psci_do_state_coordination` in that:
- The `psci_req_local_pwr_states` map is not modified if the request
  were to be denied
- The `state_info` argument is never modified since it contains the
  power states requested by the calling OS

This is conditionally compiled into the build depending on the value of
the `PSCI_OS_INIT_MODE` build option.

Change-Id: I667041c842d2856e9d128c98db4d5ae4e4552df3
Signed-off-by: Wing Li <wingers@google.com>
diff --git a/include/lib/psci/psci.h b/include/lib/psci/psci.h
index 8aaf487..d4f3670 100644
--- a/include/lib/psci/psci.h
+++ b/include/lib/psci/psci.h
@@ -277,6 +277,13 @@
 	 * for the CPU.
 	 */
 	plat_local_state_t pwr_domain_state[PLAT_MAX_PWR_LVL + U(1)];
+#if PSCI_OS_INIT_MODE
+	/*
+	 * The highest power level at which the current CPU is the last running
+	 * CPU.
+	 */
+	unsigned int last_at_pwrlvl;
+#endif
 } psci_power_state_t;
 
 /*******************************************************************************
@@ -308,7 +315,11 @@
 	void (*pwr_domain_off)(const psci_power_state_t *target_state);
 	void (*pwr_domain_suspend_pwrdown_early)(
 				const psci_power_state_t *target_state);
+#if PSCI_OS_INIT_MODE
+	int (*pwr_domain_suspend)(const psci_power_state_t *target_state);
+#else
 	void (*pwr_domain_suspend)(const psci_power_state_t *target_state);
+#endif
 	void (*pwr_domain_on_finish)(const psci_power_state_t *target_state);
 	void (*pwr_domain_on_finish_late)(
 				const psci_power_state_t *target_state);