Minor changes to documentation and comments

Fix some typos and clarify some sentences.

Change-Id: Id276d1ced9a991b4eddc5c47ad9a825e6b29ef74
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/common/aarch64/platform_mp_stack.S b/plat/common/aarch64/platform_mp_stack.S
index 972a118..f9780e8 100644
--- a/plat/common/aarch64/platform_mp_stack.S
+++ b/plat/common/aarch64/platform_mp_stack.S
@@ -14,13 +14,13 @@
 	.weak	plat_set_my_stack
 
 	/* ---------------------------------------------------------------------
-	 * When the compatility layer is disabled, the new platform APIs
-	 * viz plat_get_my_stack() and plat_set_my_stack() are
-	 * supported by the platform and the previous APIs platform_get_stack()
-	 * and platform_set_stack() are defined in terms of new APIs making use
-	 * of the fact that they are only ever invoked for the current CPU.
-	 * This is to enable components of Trusted Firmware like SPDs using the
-	 * old platform APIs to continue to work.
+	 * When the compatility layer is disabled, the platform APIs
+	 * plat_get_my_stack() and plat_set_my_stack() are supported by the
+	 * platform and the previous APIs platform_get_stack() and
+	 * platform_set_stack() are defined in terms of new APIs making use of
+	 * the fact that they are only ever invoked for the current CPU.  This
+	 * is to enable components of Trusted Firmware like SPDs using the old
+	 * platform APIs to continue to work.
 	 * --------------------------------------------------------------------
 	 */