drm/i915/dp: Use helpers to align min/max compressed BPPs

drm/i915/dp: Use helpers to align min/max compressed BPPs

The minimum/maximum compressed BPP values are aligned/bounded in
intel_dp_compute_link_bpp_limits() to the corresponding source limits.
The minimum compressed BPP value doesn't change afterwards, so no need
to align it again, remove that.

The maximum compressed BPP, which depends on the pipe BPP value still
needs to be aligned, since the pipe BPP value could change after the
above limits were computed, via intel_dp_force_dsc_pipe_bpp(). Use the
corresponding helper for this alignment instead of open-coding the same.

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20251222153547.713360-15-imre.deak@intel.com