iio: frequency: ad9832: devicetree probing support

iio: frequency: ad9832: devicetree probing support

Introduce struct for device match of_device_id to avoid relying on fallback
mechanisms, which could lead to false matches against other AD9832 variants
in the future.

Suggested-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Signed-off-by: Siddharth Menon <simeddon@gmail.com>
Link: https://patch.msgid.link/20250322163211.253009-1-simeddon@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>