virtio-sound: handle VIRTIO_SND_R_PCM_{START,STOP}

virtio-sound: handle VIRTIO_SND_R_PCM_{START,STOP}

Handle the start and stop control messages for a stream_id. This request
does nothing at the moment except for replying to it. Audio playback
or capture will be started/stopped here in follow-up commits.

Based-on: https://github.com/OpenSynergy/qemu/commit/5a2f350eec5d157b90d9c7b40a8e603f4da92471
Signed-off-by: Igor Skalkin <Igor.Skalkin@opensynergy.com>
Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <9657dbfe3cb4a48ceb033ceb5977dc08669dfefd.1698062525.git.manos.pitsidianakis@linaro.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>