drm/amd/display: decouple hw_lane_settings from dpcd_lane_settings

[why]
As DP features expands, we have encountered many situations where we
must configure a different DPCD lane setting from hw lane settings we
output.  The change is to decouple hw lane settings from dpcd lane
settings to provide flexibility to configure dpcd and hw individually.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>