Create empty data files and allow updates for the upcoming VIOT tests.

Acked-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-id: 20211210170415.583179-6-jean-philippe@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>