sound: Clean up labels of devices without origin

Sound devices may not have an origin, in that case we ended up with a
trailing " - " in the label which should not be there. Add a check that
the origin is non-null and not an empty string and only show the devices
description otherwise.
11 jobs for benzea/fix-empty-origin in 2 minutes and 47 seconds (queued for 2 seconds)
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