drm/radeon: rework audio detect (v4)

drm/radeon: rework audio detect (v4)

commit d0ea397e22f9ad0113c1dbdaab14eded050472eb upstream.

1. Always assign audio function pointers even if the display does
not support audio.  We need to properly disable the audio stream
when when using a non-audio capable monitor.  Fixes purple line
on some hdmi monitors.

2. Check if a pin is in use by another encoder before disabling
it.

v2: make sure we've fetched the edid before checking audio and
    look up the encoder before calling audio_detect since
    connector->encoder may not be assigned yet.  Separate
    pin and afmt.  They are allocated at different times and
    have no dependency on eachother.
v3: fix connector fetching in encoder functions
v4: fix missed dig->pin check in dce6_afmt_write_latency_fields

bugs:
https://bugzilla.kernel.org/show_bug.cgi?id=93701
https://bugzilla.redhat.com/show_bug.cgi?id=1236337
https://bugs.freedesktop.org/show_bug.cgi?id=91041

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>