dt-bindings: iio: vishay,vcnl4000: add interrupts property

The dtschema should list all properties, including the common ones like
interrupts.  This fixes dtbs_check warnings like:

  arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dt.yaml:
    prox@60: 'interrupt-parent', 'interrupts' do not match any of the regexes: 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200920203845.17758-1-krzk@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/light/vishay,vcnl4000.yaml

@@ -24,6 +24,10 @@ properties:
       - vishay,vcnl4020
       - vishay,vcnl4040
       - vishay,vcnl4200
+
+  interrupts:
+    maxItems: 1
+
   reg:
     maxItems: 1