- "default" is a valid argument for snd_pcm_open(), let ALSA handle that
case rather than using the first device in the list.
- Don't add "default" in the list of available devices if there is
already one.

Change-Id: Icd41aa6677923a79faf6c90d0627eedd8700b91b
Reviewed-by: Christian Stromme <christian.stromme@qt.io>