scripts/mkimage: ucode support
This is related to #11478 adding to commits to:
- 9da6b19a extends the mkimage scripts to support early initrd ucode updates
- 27a5694e 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.