- fixed building of i386-efi (32bit) live EFI iso images
- secure boot grub commands are linuxefi and initrdefi
  fix this also for oem disk images
- switch back to firmware='bios' and print a warning if uefi
  is requested on another than the x86_64 architecture. on SUSE
  we provide signed loaders and kernels for x86_64 only