doc: Add binding document for fconf.

Complete the documentation with information on how to write a DTS for
fconf. This patch adds the bindings information for dynamic
configuration properties.

Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
Change-Id: Ic6d9f927df53bb87315c23ec5a8943d0c3258d45
diff --git a/docs/components/index.rst b/docs/components/index.rst
index 49986ca..e3ce614 100644
--- a/docs/components/index.rst
+++ b/docs/components/index.rst
@@ -10,7 +10,7 @@
    arm-sip-service
    debugfs-design
    exception-handling
-   fconf
+   fconf/index
    firmware-update
    platform-interrupt-controller-API
    ras