drm/i915/dp_mst: Simplify computing the min/max compressed bpp limits

drm/i915/dp_mst: Simplify computing the min/max compressed bpp limits

Adjusting the compressed bpp range min/max limits in
intel_dp_dsc_nearest_valid_bpp() is unnecessary:

- The source/sink min/max values are enforced already by the
  link_config_limits::min_bpp_x16/max_bpp_x16 values computed early in
  intel_dp_compute_config_link_bpp_limits().
- The fixed set of valid bpps are enforced already - for all bpps in the
  min .. max range by intel_dp_dsc_valid_compressed_bpp() called from
  intel_dp_mtp_tu_compute_config().

The only thing needed is limiting max compressed bpp below the
uncompressed pipe bpp, do that one thing only instead of calling
intel_dp_dsc_nearest_valid_bpp().

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250509180340.554867-7-imre.deak@intel.com