doc: Use proper note and warning annotations

The documentation contains plenty of notes and warnings. Enable
special rendering of these blocks by converting the note prefix
into a .. note:: annotation.

Change-Id: I34e26ca6bf313d335672ab6c2645741900338822
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/getting_started/rt-svc-writers-guide.rst b/docs/getting_started/rt-svc-writers-guide.rst
index 51e9d3f..03212af 100644
--- a/docs/getting_started/rt-svc-writers-guide.rst
+++ b/docs/getting_started/rt-svc-writers-guide.rst
@@ -260,8 +260,9 @@
 ignored. The ``handle`` is returned by the SMC handler - completion of the
 handler function must always be via one of the ``SMC_RETn()`` macros.
 
-NOTE: The PSCI and Test Secure-EL1 Payload Dispatcher services do not follow
-all of the above requirements yet.
+.. note::
+   The PSCI and Test Secure-EL1 Payload Dispatcher services do not follow
+   all of the above requirements yet.
 
 Services that contain multiple sub-services
 -------------------------------------------