drm/amd/display: Fix B0 USB-C DP Alt mode

[Why]
Starting from B0, along with RDPCSTX, RDPCSPIPE registers are also used.

[How]
Make sure RDPCSPIPE registers are programmed correctly.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Zhan Liu <Zhan.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>