drm/amd/display: Handle aux_inst for connectors without DDC pin

drm/amd/display: Handle aux_inst for connectors without DDC pin

[Why & How]
Must use an alternative codepath to access AUX channel when
link->no_ddc_pin is set.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Gabe Teeger <gabe.teeger@amd.com>
Signed-off-by: Matthew Stewart <Matthew.Stewart2@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>