doc: Normalise section numbering and headings

Required work to make all documents sit at the correct levels within
the document tree and any derived content like the table of contents
and the categories in the sidebar.

Change-Id: I4885fbe30864a87c8822ee67482b71fb46a8fbc6
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/components/spd/trusty-dispatcher.rst b/docs/components/spd/trusty-dispatcher.rst
index be08570..a3cb829 100644
--- a/docs/components/spd/trusty-dispatcher.rst
+++ b/docs/components/spd/trusty-dispatcher.rst
@@ -9,7 +9,7 @@
 https://source.android.com/security/trusty
 
 Boot parameters
-===============
+---------------
 
 Custom boot parameters can be passed to Trusty by providing a platform
 specific function:
@@ -26,7 +26,7 @@
 should then be set to the size of that block.
 
 Supported platforms
-===================
+-------------------
 
 Out of all the platforms supported by Trusted Firmware-A, Trusty is only
 verified and supported by NVIDIA's Tegra SoCs.