dt-bindings: iio: adc: sophgo,cv1800b-saradc: Add Sophgo CV1800B SARADC

The Sophgo CV1800B SARADC is a Successive Approximation ADC that can be
found in the Sophgo CV1800B SoC.

Signed-off-by: Thomas Bonnefille <thomas.bonnefille@bootlin.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20240829-sg2002-adc-v5-1-aacb381e869b@bootlin.com


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