dt-bindings: iio/adc: qcom,spmi-iadc: fix reg description

The IADC register is just the base address in the SPMI PMIC and does not
include any length.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231130171628.12257-2-johan+linaro@kernel.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>