dt-bindings: iio: humidity: hdc20x0: add optional interrupts property

HDC2010 and HDC2080 humidity sensors both have an interrupt / data-ready
signal which can be used for signaling to the host.

Add binding for "interrupts" property so that boards wiring this signal
may describe the connection.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Josua Mayer <josua@solid-run.com>
Link: https://lore.kernel.org/r/20240219-iio-hdc20x0-interrupt-binding-v7-1-c8ffb39c3768@solid-run.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>