drm/amd/display: Workaround required for link training reliability

[Why]
A software workaround is required for all vendor-built cards on platform.

[How]
When performing DP link training, we must send TPS1 before DPCD:100h is
written with the proper bit rate value. This change must be applies in
ALL cases when LT happens.

Signed-off-by: David Galiffi <David.Galiffi@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>