dt-binding: clock: Add missing rk3568 cru bindings

The rk3568 cru requires a clock input and a phandle to the grf node. Add
these bindings to clear some dtbs_check warnings.

Signed-off-by: Peter Geis <pgwipeout@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220511150117.113070-2-pgwipeout@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/clock/rockchip,rk3568-cru.yaml

@@ -34,6 +34,19 @@ properties:
   "#reset-cells":
     const: 1
 
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: xin24m
+
+  rockchip,grf:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to the syscon managing the "general register files" (GRF),
+      if missing pll rates are not changeable, due to the missing pll
+      lock status.
+
 required:
   - compatible
   - reg