drm/i915/dp: Use the effective data rate for DP BW calculation

drm/i915/dp: Use the effective data rate for DP BW calculation

Use intel_dp_effective_data_rate() to calculate the required link BW for
eDP, DP-SST and MST links. This ensures that the BW is calculated the
same way for all DP output types, during mode validation as well as
during state computation. This approach also allows for accounting with
BW overheads due to the SSC, DSC, FEC being enabled on a link, as well
as due to the MST symbol alignment on the link. Accounting for these
overheads will be added by follow-up changes.

This way also computes the stream BW on a UHBR link correctly, using the
corresponding symbol size to effective data size ratio (i.e. ~97% link
BW utilization for UHBR vs. only ~80% for non-UHBR).

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20251215192357.172201-9-imre.deak@intel.com