dt-bindings: dma: apple,admac: Fix example interrupt parsing

Commit 873971f8 ("dt-bindings: dma: Add Apple ADMAC") has a warning
in its example:

Documentation/devicetree/bindings/dma/apple,admac.example.dtb: dma-controller@238200000: interrupts-extended: [[0], [4294967295, 0, 626, 4, 0, 0]] is too short
	From schema: /builds/robherring/linux-dt/Documentation/devicetree/bindings/dma/apple,admac.yaml

The problem is the number of interrupt cells can't be guessed when
there are empty '0' entries. So the example must have a valid interrupt
controller defining the number of interrupt cells.

Fixes: 873971f8 ("dt-bindings: dma: Add Apple ADMAC")
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20220614152503.1410755-1-robh@kernel.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/apple,admac.yaml

@@ -63,6 +63,11 @@ examples:
     #include <dt-bindings/interrupt-controller/apple-aic.h>
     #include <dt-bindings/interrupt-controller/irq.h>
 
+    aic: interrupt-controller {
+      interrupt-controller;
+      #interrupt-cells = <3>;
+    };
+
     admac: dma-controller@238200000 {
       compatible = "apple,t8103-admac", "apple,admac";
       reg = <0x38200000 0x34000>;