doc: Formatting fixes for readme.rst

The readme.rst file in the project root is the front-page that
is displayed on Github and if viewing the TF-A repository on
git.trustedfirmware.org in the "about" view. It now contains a
small amount of stub content, and directs readers to the
ReadTheDocs documentation via trustedfirmware.org/docs/tf-a.

The Github renderer is displaying the content fine but the cgit
viewer displays some "backlink" errors because some content
substitutions were left in place (terms surrounded by pipe
symbols), e.g. |TF-A|.

This patch removes those substitutions, that are not supported
by cgit, and also updates one heading to clarify where to find
the new docs.

Change-Id: I358451df45b8c99975ba0b6db8ea61253a10560d
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/readme.rst b/readme.rst
index f8f8daf..148d477 100644
--- a/readme.rst
+++ b/readme.rst
@@ -1,13 +1,13 @@
 Trusted Firmware-A
 ==================
 
-Trusted Firmware-A is a reference implementation of secure world software for
-`Arm A-Profile architectures`_ (Armv8-A and Armv7-A), including an
-Exception Level 3 (EL3)`Secure Monitor`_. It provides a suitable starting point
-for productization of secure world boot and runtime firmware, in either the
-|AArch32| or |AArch64| execution states.
+Trusted Firmware-A (TF-A) is a reference implementation of secure world software
+for `Arm A-Profile architectures`_ (Armv8-A and Armv7-A), including an Exception
+Level 3 (EL3) `Secure Monitor`_. It provides a suitable starting point for
+productization of secure world boot and runtime firmware, in either the AArch32
+or AArch64 execution states.
 
-|TF-A| implements Arm interface standards, including:
+TF-A implements Arm interface standards, including:
 
 -  `Power State Coordination Interface (PSCI)`_
 -  `Trusted Board Boot Requirements CLIENT (TBBR-CLIENT)`_
@@ -18,15 +18,15 @@
 The code is designed to be portable and reusable across hardware platforms and
 software models that are based on the Armv8-A and Armv7-A architectures.
 
-In collaboration with interested parties, we will continue to enhance |TF-A|
+In collaboration with interested parties, we will continue to enhance TF-A
 with reference implementations of Arm standards to benefit developers working
 with Armv7-A and Armv8-A TrustZone technology.
 
 Users are encouraged to do their own security validation, including penetration
 testing, on any secure world code derived from TF-A.
 
-Read More
----------
+More Info and Documentation
+---------------------------
 
 To find out more about Trusted Firmware-A, please `view the full documentation`_
 that is available through `trustedfirmware.org`_.