sys/sunaudio/: Fix and/or update copyright attributions (#430228).

sys/sunaudio/: Fix and/or update copyright attributions (#430228).

Original commit message from CVS:
Patch by: Brian Cameron  <brian.cameron at sun dot com>
* sys/sunaudio/gstsunaudio.c:
* sys/sunaudio/gstsunaudiomixer.c:
* sys/sunaudio/gstsunaudiomixer.h:
* sys/sunaudio/gstsunaudiomixerctrl.c:
* sys/sunaudio/gstsunaudiomixerctrl.h:
* sys/sunaudio/gstsunaudiomixertrack.h:
* sys/sunaudio/gstsunaudiosink.c:
* sys/sunaudio/gstsunaudiosink.h:
* sys/sunaudio/gstsunaudiosrc.c:
* sys/sunaudio/gstsunaudiosrc.h:
Fix and/or update copyright attributions (#430228).