virtio_mmio: add ACPI probing

Added the match table and pointers for ACPI probing to the driver.

This uses the same identifier for virt devices as being used for qemu
ARM64 ACPI support.

http://git.linaro.org/people/shannon.zhao/qemu.git/commit/d0bf1955a3ecbab4b51d46f8c5dda02b7e14a17e

Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>