Add device tree for AD4630-20 on ZedBoard

[machschmitt]

Add device tree for using AD4630-20 on Digilent ZedBoard.

PR Description

Essentially the same as AD4630-24.

$ diff arch/arm/boot/dts/xilinx/zynq-zed-adv7511-ad4630-24.dts arch/arm/boot/dts/xilinx/zynq-zed-adv7511-ad4630-20.dts                                                                              
3c3
<  * Analog Devices AD4630-24
---
>  * Analog Devices AD4630-20
8c8
<  * Copyright (C) 2022 Analog Devices Inc.
---
>  * Copyright (C) 2026 Analog Devices Inc.
99,100c99,100
<               ad4630_24: ad4630-24@0 {
<                       compatible = "adi,ad4630-24";
---
>               ad4630_20: ad4630-20@0 {
>                       compatible = "adi,ad4630-20";

PR Type

• Bug fix (a change that fixes an issue)
• New feature (a change that adds new functionality)
• Breaking change (a change that affects other repos or cause CIs to fail)

PR Checklist

• I have conducted a self-review of my own code changes
• I have compiled my changes, including the documentation
• I have tested the changes on the relevant hardware
• I have updated the documentation outside this repo accordingly
• I have provided links for the relevant upstream lore