[why]
Since for DSC MST connector's PBN is claculated differently
due to compression, we have to recalculate both PBN and
VCPI slots for that connector.

[how]
The function iterates through all the active streams to
find, which have DSC enabled, then recalculates PBN for
it and calls drm_dp_helper_update_vcpi_slots_for_dsc to
update connector's VCPI slots.

v2: - use drm_dp_mst_atomic_enable_dsc per port to
enable/disable DSC

v3: - Iterate through connector states from the state passed
    - On each connector state get stream from dc_state,
instead CRTC state
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>