dt-bindings: thermal: cooling-devices: Add missing cache related properties

The examples' cache nodes are incomplete as 'cache-unified' and
'cache-level' are required cache properties.

Acked-by: Amit Kucheria <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml

···
                     next-level-cache = <&L2_0>;
                     L2_0: l2-cache {
                             compatible = "cache";
+                            cache-unified;
+                            cache-level = <2>;
                             next-level-cache = <&L3_0>;
                             L3_0: l3-cache {
                                     compatible = "cache";
+                                    cache-unified;
+                                    cache-level = <3>;
                             };
                     };
           };