[Why]
Since introduction of patch "Query DPIA HPD status.", link detection at
boot could be accessing DPIA AUX, which will not succeed until
DMUB outbox messaging is enabled and results in below dmesg logs:

[  160.840227] [drm:amdgpu_dm_process_dmub_aux_transfer_sync [amdgpu]] *ERROR* wait_for_completion_timeout timeout!

[How]
Enable DMUB outbox messaging before link detection at boot time.
Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 6.0.x