Docs: Update code structure doc

- fix the number of CPU to 8 to avoid Sphinx crash in OpenCI

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I4f05857a639ec2609f5b21cb739a6e91e5372fc0
diff --git a/docs/integration_guide/index.rst b/docs/integration_guide/index.rst
index 36a4930..821d894 100644
--- a/docs/integration_guide/index.rst
+++ b/docs/integration_guide/index.rst
@@ -4,15 +4,16 @@
 The purpose of this document is to provide a guide on how to integrate TF-M
 with other hardware platforms and operating systems.
 
-
 .. toctree::
     :maxdepth: 1
 
-    SPM Backends <spm_backends.rst>
-    NS client integration <non-secure_client_extension_integration_guide.rst>
+    Source Structure        <source_structure/index>
+    SPM Backends            <spm_backends.rst>
+    NS client integration   <non-secure_client_extension_integration_guide.rst>
     OS migration to Armv8-M <os_migration_guide_armv8m.rst>
-    tfm_fpu_support
-    Secure Interrupt <tfm_secure_irq_integration_guide.rst>
+    Floating-Point Support  <tfm_fpu_support.rst>
+    Secure Interrupt        <tfm_secure_irq_integration_guide.rst>
+    Platform Provisioning   <platform_provisioning.rst>
 
 .. toctree::
     :maxdepth: 2
@@ -20,7 +21,6 @@
     platform/index
     services/index
 
-
 *****************
 How to build TF-M
 *****************