DTB (FDT) parsing & patching, choosing device tree libraries

[orangecms]

For dtb based platforms, we need the ability to pass memory configuration (DRAM size, notably), which is determined at runtime.

We do have a small library around device trees already for layoutflash, our internal library for the DTFS (device tree file system), currently depending on repnop/fdt.

RustSBI has another library, supporting serde: https://github.com/rustsbi/serde-device-tree

[orangecms]

related: #498

[rmsyn]

FWIW my vote is for https://github.com/repnop/fdt, no dependencies, does the job.

[orangecms]

https://github.com/rivosinc/salus/tree/main/device-tree/src

also for reference - based on https://github.com/rs-embedded/fdt-rs