dt-bindings: devfreq: tegra30-actmon: Add cooling-cells

The ACTMON watches activity of memory clients. Decisions about a minimum
required frequency are made based on the info from ACTMON. We can use
ACTMON as a thermal cooling device by limiting the required frequency.
Document new cooling-cells property of NVIDIA Tegra ACTMON hardware unit.

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

Documentation/devicetree/bindings/devfreq/nvidia,tegra30-actmon.yaml

@@ -63,6 +63,9 @@ properties:
       Should contain freqs and voltages and opp-supported-hw property, which
       is a bitfield indicating SoC speedo ID mask.
 
+  "#cooling-cells":
+    const: 2
+
 required:
   - compatible
   - reg
@@ -74,6 +77,7 @@ required:
   - interconnects
   - interconnect-names
   - operating-points-v2
+  - "#cooling-cells"
 
 additionalProperties: false
 
@@ -118,4 +122,5 @@ examples:
         operating-points-v2 = <&dvfs_opp_table>;
         interconnects = <&mc TEGRA30_MC_MPCORER &emc>;
         interconnect-names = "cpu-read";
+        #cooling-cells = <2>;
     };