dt-bindings: iio: Add adis16550 bindings

Document the ADIS16550 device devicetree bindings.

Co-developed-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: Robert Budai <robert.budai@analog.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250217105753.605465-5-robert.budai@analog.com


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