PSCI: Decouple PSCI stat residency calculation from PMF

This patch introduces the following three platform interfaces:

* void plat_psci_stat_accounting_start(const psci_power_state_t *state_info)

  This is an optional hook that platforms can implement in order
  to perform accounting before entering a low power state.  This
  typically involves capturing a timestamp.

* void plat_psci_stat_accounting_stop(const psci_power_state_t *state_info)

  This is an optional hook that platforms can implement in order
  to perform accounting after exiting from a low power state.  This
  typically involves capturing a timestamp.

* u_register_t plat_psci_stat_get_residency(unsigned int lvl,
	const psci_power_state_t *state_info,
	unsigned int last_cpu_index)

  This is an optional hook that platforms can implement in order
  to calculate the PSCI stat residency.

If any of these interfaces are overridden by the platform, it is
recommended that all of them are.

By default `ENABLE_PSCI_STAT` is disabled.  If `ENABLE_PSCI_STAT`
is set but `ENABLE_PMF` is not set then an alternative PSCI stat
collection backend must be provided.  If both are set, then default
weak definitions of these functions are provided, using PMF to
calculate the residency.

NOTE: Previously, platforms did not have to explicitly set
`ENABLE_PMF` since this was automatically done by the top-level
Makefile.

Change-Id: I17b47804dea68c77bc284df15ee1ccd66bc4b79b
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
diff --git a/lib/psci/psci_private.h b/lib/psci/psci_private.h
index 781b3b5..ca8291e 100644
--- a/lib/psci/psci_private.h
+++ b/lib/psci/psci_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -35,7 +35,6 @@
 #include <bakery_lock.h>
 #include <bl_common.h>
 #include <cpu_data.h>
-#include <pmf.h>
 #include <psci.h>
 #include <spinlock.h>
 
@@ -106,15 +105,6 @@
 #define is_cpu_standby_req(is_power_down_state, retn_lvl) \
 		(((!(is_power_down_state)) && ((retn_lvl) == 0)) ? 1 : 0)
 
-/* Following are used as ID's to capture time-stamp */
-#define PSCI_STAT_ID_ENTER_LOW_PWR		0
-#define PSCI_STAT_ID_EXIT_LOW_PWR		1
-#define PSCI_STAT_TOTAL_IDS			2
-
-/* Declare PMF service functions for PSCI */
-PMF_DECLARE_CAPTURE_TIMESTAMP(psci_svc)
-PMF_DECLARE_GET_TIMESTAMP(psci_svc)
-
 /*******************************************************************************
  * The following two data structures implement the power domain tree. The tree
  * is used to track the state of all the nodes i.e. power domain instances
@@ -246,8 +236,7 @@
 void psci_stats_update_pwr_down(unsigned int end_pwrlvl,
 			const psci_power_state_t *state_info);
 void psci_stats_update_pwr_up(unsigned int end_pwrlvl,
-			const psci_power_state_t *state_info,
-			unsigned int flags);
+			const psci_power_state_t *state_info);
 u_register_t psci_stat_residency(u_register_t target_cpu,
 			unsigned int power_state);
 u_register_t psci_stat_count(u_register_t target_cpu,