dt-bindings: iio: adc: ti,ads1015: Document optional interrupt line

The ADS1015 can have optional IRQ line connected, document it in the DT bindings.
Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230921192420.70643-1-marex@denx.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/ti,ads1015.yaml

@@ -23,6 +23,9 @@ properties:
   reg:
     maxItems: 1
 
+  interrupts:
+    maxItems: 1
+
   "#address-cells":
     const: 1