drm/amd/display: Use the maximum link setting which EDP reported.

Signed-off-by: Hugo Hu <hugo.hu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>