fix: remove capture mixer setup from audio_init
On the 11e Yoga Gen 5, enabling capture switches/volume at boot (before
any capture PCM stream is open) puts the HDA codec into a bad state.
The original working code (90d8beeee) only touched playback controls
in audio_init. Capture mixer was added later in 693ea22c8.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>