Enables enformement support for EFI bootable images

[riccardomanfrin]

Currently the option is not managed

Enable flag with

resource "virtualbox_vm" "node" {
  count     = 1
  name      = format("node-%02d", count.index + 1)
  image     = yourova.ova"
  cpus      = 2
  memory    = "512 mib"
  ## **** see here ****
  firmware  = "efi"

  network_adapter {
    type           = "bridged"
    host_interface = "enp0s31f6"
  }
}

should give you this under "System"