hw/audio/virtio-sound: return correct command response size

hw/audio/virtio-sound: return correct command response size

The payload size returned by command VIRTIO_SND_R_PCM_INFO is
wrong. The code in process_cmd() assumes that all commands
return only a virtio_snd_hdr payload, but some commands like
VIRTIO_SND_R_PCM_INFO may return an additional payload.

Add a zero initialized payload_size variable to struct
virtio_snd_ctrl_command to allow for additional payloads.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20240218083351.8524-1-vr_qemu@t-online.de>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 633487df8d303b37a88584d5a57a39dbcd91c7bf)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>