[Task]: Convert recent (2024.01+) u-boot null-patches into `dt/` and `defconfig/` bare patches

### Task description

The Armbian patching utility supports adding files directly instead of requiring null-patches (patches that add complete files). Null-patches are unwieldy, forcing developers to generate patches for no reason.

We have such setup for many kernels, but also for the vendor rk35xx u-boot, as can be seen in `patch/u-boot/legacy/u-boot-radxa-rk35xx/0000.patching_config.yaml` (and `patch/u-boot/legacy/u-boot-radxa-rk35xx/defconfig` and `patch/u-boot/legacy/u-boot-radxa-rk35xx/dt` folders).

Let's replicate this setup (1 .yaml configuration file and 2 folders, one for DTS and one for defconfig) so we can get rid of null patches for the mainline u-boot as well.

Let's begin with the most recent u-boot (`v2025.01`) and work our way back; that way when new contributions begin they've a good example to follow.