rename option to new image.baseName

[onny]

Description of changes

When building riscv VisionFive2 image or cross-compiling to it, following warning appears: evaluation warning: Obsolete option "sdImage.imageBaseName" is used. It was renamed to "image.baseName".

Things done

• [ ] Tested the changes in your own NixOS Configuration
• [ ] Tested the changes end-to-end by using your fork of nixos-hardware and importing it via <nixos-hardware> or Flake input