drm/i915/dp: compute config for 128b/132b SST w/o DSC

Enable basic 128b/132b SST functionality without compression. Reuse
intel_dp_mtp_tu_compute_config() to figure out the TU after we've
determined we need to use an UHBR rate.

It's slightly complicated as the M/N computation is done in different
places in MST and SST paths, so we need to avoid trashing the values
later for UHBR.

If uncompressed UHBR fails, we drop to compressed non-UHBR, which is
quite likely to fail as well. We still lack 128b/132b SST+DSC.

We need mst_master_transcoder also for 128b/132b SST. Use cpu_transcoder
directly. Enhanced framing is "don't care" for 128b/132b link.

v2: mst_master_transcoder, enhanced framing (Imre)

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/084e4e05bf25a5dd396dd391014943d42b11c88d.1735912293.git.jani.nikula@intel.com