dt-bindings: devfreq: event: rockchip,dfi: Add rk3568 support

This adds the rockchip,rk3568-dfi compatible to the binding. Make clocks
optional for this SoC as the RK3568 doesn't have a kernel controllable
PCLK.

Link: https://lore.kernel.org/all/[e-mail]/
Reviewed-by: Conor Dooley <[e-mail]>
Acked-by: Chanwoo Choi <[e-mail]>
Signed-off-by: Sascha Hauer <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

Documentation/devicetree/bindings/devfreq/event/rockchip,dfi.yaml

···
   compatible:
     enum:
       - rockchip,rk3399-dfi
+      - rockchip,rk3568-dfi
 
   clocks:
     maxItems: 1
···
 
 required:
   - compatible
-  - clocks
-  - clock-names
   - interrupts
   - reg
+
+if:
+  properties:
+    compatible:
+      contains:
+        enum:
+          - rockchip,rk3399-dfi
+
+then:
+  required:
+    - clocks
+    - clock-names
 
 additionalProperties: false