docs: Fixes to platform-migration-guide.md

This patch corrects some typos in the platform migration guide. More                                                                                                                                                                                                              
importantly, the commit ID of the patch that implements migration of ARM
Reference platforms to the new platform API has been corrected.

Change-Id: Ib0109ea42c3d2bad2c6856ab725862652da7f3c8
diff --git a/docs/platform-migration-guide.md b/docs/platform-migration-guide.md
index 806fa19..f6790ef 100644
--- a/docs/platform-migration-guide.md
+++ b/docs/platform-migration-guide.md
@@ -57,7 +57,7 @@
 described in section 4.2 of [PSCI], could contain a core or a logical group
 of cores (a cluster) which share some state on which power management
 operations can be performed. The existing affinity instance based APIs
-`plat_get_aff_count()` and `plat_get_aff_count()` are deprecated. The new
+`plat_get_aff_count()` and `plat_get_aff_state()` are deprecated. The new
 platform interfaces that are introduced for this framework are:
 
 *   `plat_core_pos_by_mpidr()`
@@ -100,8 +100,8 @@
 used to describe the composite power states specific to a platform. The existing
 PSCI state coordination had the limitation that it operates on a run/off
 granularity of power states and it did not interpret the state-ID field. This
-was acceptable as the specification requirement in PSCI 0.2. The framework's
-approach to coordination only requires maintaining a reference
+was acceptable as the specification requirement in PSCI 0.2 and the framework's
+approach to coordination only required maintaining a reference
 count of the number of cores that have requested the cluster to remain powered.
 
 In the PSCI 1.0 specification, this approach is non optimal. If composite
@@ -173,7 +173,8 @@
 
 The PSCI 1.0 implementation depends on the `validate_power_state` handler to
 convert the power-state parameter (possibly encoding a composite power state)
-passed in a PSCI `CPU_SUSPEND` to the `psci_power_state` format.
+passed in a PSCI `CPU_SUSPEND` to the `psci_power_state` format. This handler
+is now mandatory for PSCI `CPU_SUSPEND` support.
 
 The `plat_psci_ops` handlers, `pwr_domain_off` and `pwr_domain_suspend`, are
 passed the target local state for each affected power domain. The platform
@@ -209,7 +210,7 @@
 ![Image 1](diagrams/psci-suspend-sequence.png?raw=true)
 
 Refer [plat/arm/board/fvp/fvp_pm.c] for the implementation details of
-these handlers for the FVP. The commit b6df6ccbc88cc14592f5e603ef580d3cbf4733c3
+these handlers for the FVP. The commit 38dce70f51fb83b27958ba3e2ad15f5635cb1061
 demonstrates the migration of ARM reference platforms to the new platform API.
 
 
@@ -259,7 +260,7 @@
 
 The compatibility layer dynamically constructs the new topology
 description array by querying the platform using `plat_get_aff_count()`
-and `plat_get_aff_count()` APIs. The linear index returned by
+and `plat_get_aff_state()` APIs. The linear index returned by
 `platform_get_core_pos()` is used as the core index for the cores. The
 higher level (non-core) power domain nodes must know the cores contained
 within its domain. It does so by storing the core index of first core