doc: Reformat RST content for Sphinx rendering

Some existing RST files contain formatting errors that will cause
Sphinx to generate warnings.

Change-Id: I714136d1ea5b645eaa55dd304fb56d5b5fd18ee1
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/porting-guide.rst b/docs/porting-guide.rst
index 9759c98..ba9b9aa 100644
--- a/docs/porting-guide.rst
+++ b/docs/porting-guide.rst
@@ -1,12 +1,5 @@
-Trusted Firmware-A Tests - Porting Guide
-========================================
-
-.. section-numbering::
-    :suffix: .
-
-.. contents::
-
---------------
+Porting Guide
+=============
 
 Introduction
 ------------