drm/radeon: add audio support for DCE6/8 GPUs (v12)

Similar to DCE4/5, but supports multiple audio pins
which can be assigned per afmt block.

v2: rework the driver to handle more than one audio
pin.
v3: try different dto reg
v4: properly program dto
v5 (ck): change dto programming order
v6: program speaker allocation block
v7: rebase
v8: rebase on Rafał's changes
v9: integrated Rafał's comments, update to latest
    drm_edid_to_speaker_allocation API
v10: add missing line break in error message
v11: add back audio enabled messages
v12: fix copy paste typo in r600_audio_enable

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Rafał Miłecki <zajec5@gmail.com>