drm/amd/display: Add DP 2.0 SST DC Support

1. Retrieve 128/132b link cap.
2. 128/132b link training and payload allocation.
3. UHBR10 link rate support.

[squash in warning fixes - Alex]

Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>