fix(dracut.sh): handle imagebase for uefi

fix(dracut.sh): handle imagebase for uefi

* UEFI creation didn't handle the ImageBase data for the PE file
  generation. Create an UKI thanks a stub file with a non zero BaseImage
  logs some warning ans generate a bad file offset management. The efi
  becomes unloadable.
* This commit parse the PE file header, get the data and apply the
  ImageBase on the objcopy command.

Fixes dracutdevs#2284

Signed-off-by: Valentin Lefebvre <valentin.lefebvre@suse.com>