docs(psci): expound runtime instrumentation docs

Change-Id: I3c30b44d4196c30fd07373282150e543959fce1a
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
diff --git a/docs/perf/index.rst b/docs/perf/index.rst
index bccad00..b83c6e3 100644
--- a/docs/perf/index.rst
+++ b/docs/perf/index.rst
@@ -5,10 +5,12 @@
    :maxdepth: 1
    :caption: Contents
 
+   psci-performance-instr
    psci-performance-juno
+   psci-performance-methodology
    tsp
    performance-monitoring-unit
 
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-*Copyright (c) 2019-2020, Arm Limited. All rights reserved.*
+*Copyright (c) 2019-2023, Arm Limited. All rights reserved.*