iio: adc: adi-axi-adc: set data format

Add support for selecting the data format within the AXI ADC ip.

Add separate complatible string for the custom AD485X IP and implement
the necessary changes.

Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Link: https://patch.msgid.link/20250214131955.31973-7-antoniu.miclaus@analog.com


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