WIP: scripts/mkimage: ucode support
This is related to #11478 adding to commits to:
- 9b9e4b10 extends the mkimage scripts to support early initrd ucode updates
- 0c69489b adds a ucode profile based on extended
This MR should be used as a base for further discussions. It currently only works for Intel CPU ucode updates since there is no package providing an early initrd for AMD CPU ucode, yet.