doc: debugfs remove references section and add topic to components index

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I8c2e6dc98f2f30a81f4f80cc0ca1232fed7a53c9
diff --git a/docs/components/index.rst b/docs/components/index.rst
index f1904c0..8442583 100644
--- a/docs/components/index.rst
+++ b/docs/components/index.rst
@@ -8,6 +8,7 @@
 
    spd/index
    arm-sip-service
+   debugfs-design
    exception-handling
    firmware-update
    platform-interrupt-controller-API