[TRACKER] HDMI/DP audio support

[jannau]

This is a tracker bug for issues with DCP audio for HDMI / DP audio.

Initially this bug is used to track issues which need to be resolved before enabling HDMI/DP audio by default. It is already present and can be enabled with apple_dcp.hdmi_audio=1 on the kernel command line for testing.

When reporting issue discovered while testing include in report the test device, the port used for testing and the used display (preferable with its EDID which is available via /sys/class/drm/card2-HDMI-A-1/edid or similar).

Open issues

• alsa ucm config for 5.1 / 7.1 channel configs
• Add port / display device identifier to the sound card name
• fix afk service shutdown on hotplug
• other issues @asahilina mentioned

Resolved issues

• DCPAVAudioInterface service is recreated on display power cycles on some devices (resolved with 0bf2b77)