Fix broken links to various sections across docs

These broken links were found with the help of this command:
$> sphinx-build -M linkcheck . build

A sample broken link is reported as follows:
(line   80) -local-   firmware-design.rst#secure-el1-payloads-and-dispatchers

Change-Id: I5dcefdd4b8040908658115647e957f6c2c5da7c2
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/docs/components/debugfs-design.rst b/docs/components/debugfs-design.rst
index 2096bdb..2536515 100644
--- a/docs/components/debugfs-design.rst
+++ b/docs/components/debugfs-design.rst
@@ -80,8 +80,8 @@
 The communication with the 9p layer in BL31 is made through an SMC conduit
 (`SMC Calling Convention`_), using a specific SiP Function Id. An NS
 shared buffer is used to pass path string parameters, or e.g. to exchange
-data on a read operation. Refer to `ARM SiP Services`_ for a description
-of the SMC interface.
+data on a read operation. Refer to :ref:`ARM SiP Services <arm sip services>`
+for a description of the SMC interface.
 
 Security considerations
 -----------------------