CRAS: rstream - Go back to one shm area.

Now that unified streams have been removed there is no need for
separate input and output shm areas.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
CRAS: iodev_list - use define for "no device"

A zero index means "no device", use a #define for this.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
wip - add dev_mix thing