dt-bindings: thermal: armada: add reference to new bindings

New bindings (using a syscon) are available for AP806 and CP110
compatibles. Add a reference to these files from the original
documentation.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Documentation/devicetree/bindings/thermal/armada-thermal.txt

@@ -10,6 +10,11 @@ Required properties:
     * marvell,armada-ap806-thermal
     * marvell,armada-cp110-thermal
 
+Note: these bindings are deprecated for AP806/CP110 and should instead
+follow the rules described in:
+Documentation/devicetree/bindings/arm/marvell/ap806-system-controller.txt
+Documentation/devicetree/bindings/arm/marvell/cp110-system-controller.txt
+
 - reg: Device's register space.
   Two entries are expected, see the examples below. The first one points
   to the status register (4B). The second one points to the control