dt-bindings: mediatek: Add #reset-cells to mmsys system controller

The mmsys system controller exposes a set of memory client resets and
needs to specify the #reset-cells property in order to advertise the
number of cells needed to describe each of the resets.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210930103105.v4.2.I3f7f1c9a8e46be07d1757ddf4e0097535f3a7d41@changeid
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.yaml

@@ -43,6 +43,9 @@ properties:
   "#clock-cells":
     const: 1
 
+  '#reset-cells':
+    const: 1
+
 required:
   - compatible
   - reg
@@ -56,4 +59,5 @@ examples:
         compatible = "mediatek,mt8173-mmsys", "syscon";
         reg = <0x14000000 0x1000>;
         #clock-cells = <1>;
+        #reset-cells = <1>;
     };