cmd: dtimg: add get by id and set dt info to env
This adds support for getting dt blob via id. That can be used optionally be adding another argument at the currently supported sub commands.
Additionally, it sets dt blob info to env so it can be validated further if needed (for example if by index is used). id --> fdt_id rev --> fdt_rev custom[X] --> fdt_customX
Edited by CTCaer