[salt-formulas] Add & enable armband formula

[salt-formulas] Add & enable armband formula

AArch64 specific formula, mostly tweaking nova conf / installing
virtualization layer prerequisites:
- install qemu-efi;
- install vgabios;
- fix missing link for vgabios binary blob;
- nova conf: cpu_model=cortex-a57 (only for virtual deploys);
- nova conf: virt_type=qemu (only for virtual deploys);
- nova compute conf: virt_type=qemu (only for virtual deploys);
- nova conf: pointer_model=ps2mouse since AArch64 has no USB tablet;

[1] https://github.com/openstack/nova/commit/f0f0953

Change-Id: I40515bdbd941850b103a86d51b347cc8610f5741
Signed-off-by: Guillermo Herrero <Guillermo.Herrero@enea.com>
Signed-off-by: Charalampos Kominos <Charalampos.Kominos@enea.com>
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>