Add optional PSCI STAT residency & count functions

This patch adds following optional PSCI STAT functions:

- PSCI_STAT_RESIDENCY: This call returns the amount of time spent
  in power_state in microseconds, by the node represented by the
  `target_cpu` and the highest level of `power_state`.

- PSCI_STAT_COUNT: This call returns the number of times a
  `power_state` has been used by the node represented by the
  `target_cpu` and the highest power level of `power_state`.

These APIs provides residency statistics for power states that has
been used by the platform. They are implemented according to v1.0
of the PSCI specification.

By default this optional feature is disabled in the PSCI
implementation. To enable it, set the boolean flag
`ENABLE_PSCI_STAT` to 1. This also sets `ENABLE_PMF` to 1.

Change-Id: Ie62e9d37d6d416ccb1813acd7f616d1ddd3e8aff
diff --git a/include/bl31/services/psci.h b/include/bl31/services/psci.h
index 95e7780..20aa52e 100644
--- a/include/bl31/services/psci.h
+++ b/include/bl31/services/psci.h
@@ -80,6 +80,10 @@
 #define PSCI_FEATURES			0x8400000A
 #define PSCI_SYSTEM_SUSPEND_AARCH32	0x8400000E
 #define PSCI_SYSTEM_SUSPEND_AARCH64	0xc400000E
+#define PSCI_STAT_RESIDENCY_AARCH32	0x84000010
+#define PSCI_STAT_RESIDENCY_AARCH64	0xc4000010
+#define PSCI_STAT_COUNT_AARCH32		0x84000011
+#define PSCI_STAT_COUNT_AARCH64		0xc4000011
 
 /* Macro to help build the psci capabilities bitfield */
 #define define_psci_cap(x)		(1 << (x & 0x1f))
@@ -87,7 +91,11 @@
 /*
  * Number of PSCI calls (above) implemented
  */
+#if ENABLE_PSCI_STAT
+#define PSCI_NUM_CALLS			22
+#else
 #define PSCI_NUM_CALLS			18
+#endif
 
 /*******************************************************************************
  * PSCI Migrate and friends
@@ -274,6 +282,11 @@
 	int (*validate_ns_entrypoint)(uintptr_t ns_entrypoint);
 	void (*get_sys_suspend_power_state)(
 				    psci_power_state_t *req_state);
+	int (*get_pwr_lvl_state_idx)(plat_local_state_t pwr_domain_state,
+				    int pwrlvl);
+	int (*translate_power_state_by_mpidr)(u_register_t mpidr,
+				    unsigned int power_state,
+				    psci_power_state_t *output_state);
 } plat_psci_ops_t;
 
 /*******************************************************************************