fix(docs): replace deprecated urls under tfa/docs

Fixed internal links refrenced inside tfa/docs.
Followed https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#ref-role
for instrustion on how to link sections within other documents.

Signed-off-by: Thaddeus Serna <thaddeus.gonzalez-serna@arm.com>
Change-Id: I8e7c090d98951b1e3d393ab5b1d6bcdaa1865c6f
diff --git a/docs/perf/psci-performance-n1sdp.rst b/docs/perf/psci-performance-n1sdp.rst
index 70a1436..ae1b89b 100644
--- a/docs/perf/psci-performance-n1sdp.rst
+++ b/docs/perf/psci-performance-n1sdp.rst
@@ -10,8 +10,8 @@
 - TFTF [`v2.9-rc0`_]
 - SCP/MCP `Prebuilt Images`_
 
-Please see the Runtime Instrumentation `Testing Methodology`_ page for more
-details.
+Please see the Runtime Instrumentation :ref:`Testing Methodology
+<Runtime Instrumentation Methodology>` page for more details.
 
 Procedure
 ---------
@@ -200,4 +200,3 @@
 .. _user guide: https://gitlab.arm.com/arm-reference-solutions/arm-reference-solutions-docs/-/blob/master/docs/n1sdp/user-guide.rst
 .. _Prebuilt Images:  https://downloads.trustedfirmware.org/tf-a/css_scp_2.11.0/n1sdp/release/
 .. _N1SDP: https://developer.arm.com/documentation/101489/latest
-.. _Testing Methodology: ../perf/psci-performance-methodology.html
\ No newline at end of file