The driver always opens the audio device in duplex mode, i.e.,
playback and recording. Setting the 'playback' or 'recording' attribute
only influnces the service announcement. Due to changes made in a more
recent OpenBSD release recording must be set enabled explicitly anyway.
Since we already provide the interface that mirrors the one used by
OpenBSD 1:1 in the configuration use that and the remove the additional
config attributes.
Fixes#3757.
f1427fc02a