dt-bindings: iio: adc: adi,ad4030: Add ADAQ4216 and ADAQ4224

dt-bindings: iio: adc: adi,ad4030: Add ADAQ4216 and ADAQ4224

ADAQ4216 and ADAQ4224 are similar to AD4030 except that ADAQ devices have a
PGA (programmable gain amplifier) that scales the input signal prior to it
reaching the ADC inputs. The PGA is controlled through a couple of pins (A0
and A1) that set one of four possible signal gain configurations.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>