drm/amd/display: Enable aux transfer path via dmub for dp tunneling

drm/amd/display: Enable aux transfer path via dmub for dp tunneling

[Why]
Aux transfer retries path does not support dp tunneling.

[How]
Based on ddc pin check, aux will be issued in legacy path or DMUB.

Signed-off-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Reviewed-by: Eric Yang <eric.yang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>