SPM: Set STATIC_HANDLE_IDX_BIT_WIDTH as 5

The current used number of stateless handle is 32, which occupies only
5 bits. So change STATIC_HANDLE_IDX_BIT_WIDTH from 8 to 5 to avoid
unnecessary static handle index validation because it can not be larger
than 32.

Related document is also updated in this patch.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I5bb9119ff7c03cc6a067fb291e3cbff2627ba49d
diff --git a/docs/design_docs/services/stateless_rot_service.rst b/docs/design_docs/services/stateless_rot_service.rst
index 964c18c..96b65ce 100644
--- a/docs/design_docs/services/stateless_rot_service.rst
+++ b/docs/design_docs/services/stateless_rot_service.rst
@@ -46,7 +46,9 @@
       - reserved
     * - bit 15 - bit 8
       - service version requested by client - for client version check
-    * - bit 7 - bit 0
+    * - bit 7 - bit 5
+      - reserved
+    * - bit 4 - bit 0
       - the handle index, [0, 31]
 
 Since connection-based services and stateless services share the same PSA API
@@ -84,7 +86,7 @@
 ==========================
 
 This chapter describes the changes in programming API for stateless services.
-The following APIs' bebavious and message data structure members are updated to
+The following APIs' behavious and message data structure members are updated to
 support the stateless service.
 
 psa_connect()