UAPI Changes: None

Cross-subsystem Changes: None

Core Changes: Fixed some issues introduced by commit cd82d82cbc04
("drm/dp_mst: Add branch bandwidth validation to MST atomic check"),
which caused the DP MST helpers to incorrectly reject display
configurations in drm_dp_mst_atomic_check() as a result of
miscalculating the available bandwidth. Additionally, another issue that
was required for this to work was fixed where we would reject display
configurations because we would accidentally expose MST connectors to
userspace before having probed their available bandwidth.

Driver Changes: None