xilinx: Enable virtio mmio transport and devices

Qemu can create virtio mmio transports and passing devices through it
that's why enable virtio by default on all arm64 based SoCs.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/a2ee18e7e8c1881ce72c5cd13127794a02410696.1679583129.git.michal.simek@amd.com