dt-bindings: iio: adc: add ad485x axi variant

dt-bindings: iio: adc: add ad485x axi variant

Add a new compatible and related bindings for the fpga-based
AD485x AXI IP core, a variant of the generic AXI ADC IP.

The AXI AD485x IP is a very similar HDL (fpga) variant of the
generic AXI ADC IP, intended to control ad485x family.

Although this is not preferred, the wildcard naming is used to
match the published firmware under the same name.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Link: https://patch.msgid.link/20250214131955.31973-6-antoniu.miclaus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>