drm/amd/display: consider DSC pass-through during mode validation

drm/amd/display: consider DSC pass-through during mode validation

Add a mode validation routine for DSC pass-through. Both the link from
source to hub, and the link from hub to monitor are checked, according
to the current link training result and full pbn returned by enum path
resource sideband message.

Pick up the minimum value as the bandwidth bottleneck for the end to
end link bandwidth constraint, and check if the maximum DSC decompression
bandwidth can fit.

v2: squash in DSC CONFIG_DRM_AMD_DC_DCN compilation fix (Hamza)

Co-authored-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>