drm/amd/display: plumbing to allow easy print of HW state for DTN

Signed-off-by: Tony Cheng <tony.cheng@amd.com>
Reviewed-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>