psci: update docs with status of cpu_suspend api

This patch makes changes to the documents to reflect the current
state of play of the psci cpu_suspend function.

Change-Id: I086509fb75111b6e9f93b7f6dbcd33cc4591b9f3
diff --git a/docs/change-log.md b/docs/change-log.md
index 5a9bdb3..4e5b9aa 100644
--- a/docs/change-log.md
+++ b/docs/change-log.md
@@ -59,6 +59,20 @@
 *   A restriction in the FVP code which did not allow the non-secure entrypoint
     to lie outside the DRAM has been removed.
 
+*   The PSCI CPU_SUSPEND api has been stabilised to an extent where it can be
+    used for entry into power down states with the following restrictions:
+    -   Entry into standby states is not supported.
+    -   The api is only supported on the AEMv8 Base FVP.
+
+
+*   The PSCI AFFINITY_INFO api has undergone limited testing on the AEMv8 Base
+    FVP to allow experimental use.
+
+*   Locks corresponding to each affinity level are acquired and released in
+    the correct sequence in the PSCI implementation. Invocation of the PSCI
+    CPU_SUSPEND and CPU_OFF apis simultaneously across cpus & clusters should
+    not result in unexpected behaviour.
+
 ARM Trusted Firmware - version 0.2
 ==================================