hw/audio/virtio-snd-pci: fix the PCI class code

hw/audio/virtio-snd-pci: fix the PCI class code

The virtio sound device is currently an unclassified PCI device.

~> sudo lspci -s '00:02.0' -v -nn | head -n 2
00:02.0 Unclassified device [00ff]:
 Red Hat, Inc. Device [1af4:1059] (rev 01)
        Subsystem: Red Hat, Inc. Device [1af4:1100]

Set the correct PCI class code to change the device to a
multimedia audio controller.

~> sudo lspci -s '00:02.0' -v -nn | head -n 2
00:02.0 Multimedia audio controller [0401]:
 Red Hat, Inc. Device [1af4:1059] (rev 01)
        Subsystem: Red Hat, Inc. Device [1af4:1100]

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20231107185034.6434-1-vr_qemu@t-online.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>