dt-bindings: clock: mediatek: Document reset cells for MT8188 sys

The MT8188 sys clocks embed a reset controller: add #reset-cells
to the binding to allow using resets.

Fixes: 1086a5310f9c ("dt-bindings: clock: mediatek: Add new MT8188 clock")
Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Acked-by: Conor Dooley <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

Documentation/devicetree/bindings/clock/mediatek,mt8188-sys-clock.yaml

···
   '#clock-cells':
     const: 1
 
+  '#reset-cells':
+    const: 1
+
 required:
   - compatible
   - reg