sound: Rename SndWorker to SndChannel
sound: Rename SndWorker to SndChannel

SndWorker has been historically based on RedChannel, initial git commit
has:
struct SndWorker {
     Channel base;
     ...
};

Signed-off-by: Frediano Ziglio <55d48b080b2e443e395cde84d2c83b135a4ff48e@redhat.com>
Acked-by: Christophe Fergeau <05b95054a663c388a4e33d95828cb30f0370f8ef@redhat.com>

fgouget/spice,fgouget/spice,fgouget/spice,fgouget/spice