dt-bindings: iio: adc: zynqmp_ams: Add clock entry

The AMS driver DT binding was missing the clock entry, which is actually
mandatory according to the driver implementation. Add this in.

Fixes: 39dd2d1e25 ("dt-bindings: iio: adc: Add Xilinx AMS binding documentation")
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/20220127173450.3684318-2-robert.hancock@calian.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/xlnx,zynqmp-ams.yaml

@@ -92,6 +92,10 @@ properties:
     description: AMS Controller register space
     maxItems: 1
 
+  clocks:
+    items:
+      - description: AMS reference clock
+
   ranges:
     description:
       Maps the child address space for PS and/or PL.
@@ -181,12 +185,15 @@ properties:
 required:
   - compatible
   - reg
+  - clocks
   - ranges
 
 additionalProperties: false
 
 examples:
   - |
+    #include <dt-bindings/clock/xlnx-zynqmp-clk.h>
+
     bus {
         #address-cells = <2>;
         #size-cells = <2>;
@@ -196,6 +203,7 @@ examples:
             interrupt-parent = <&gic>;
             interrupts = <0 56 4>;
             reg = <0x0 0xffa50000 0x0 0x800>;
+            clocks = <&zynqmp_clk AMS_REF>;
             #address-cells = <1>;
             #size-cells = <1>;
             #io-channel-cells = <1>;