hw/arm/virt: Declare virtio-mmio as dma cache coherent in ACPI

hw/arm/virt: Declare virtio-mmio as dma cache coherent in ACPI

Virtio-mmio devices can directly access guest memory and do so in cache
coherent fashion. Tell the guest about that fact when it's using ACPI.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Shannon Zhao <shannon.zhao@linaro.org>
Message-id: 1486644810-33181-3-git-send-email-agraf@suse.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>