drm/dp: Add helpers to query the branch DSC max throughput/line-width

drm/dp: Add helpers to query the branch DSC max throughput/line-width

Add helpers to query the DP DSC sink device's per-slice throughput as
well as a DSC branch device's overall throughput and line-width
capabilities.

v2 (Ville):
- Rename pixel_clock to peak_pixel_rate, document what the value means
  in case of MST tiled displays.
- Fix name of drm_dp_dsc_branch_max_slice_throughput() to
  drm_dp_dsc_sink_max_slice_throughput().
v3:
- Fix the DSC branch device minimum valid line width value from 2560
  to 5120 pixels.
- Fix drm_dp_dsc_sink_max_slice_throughput()'s pixel_clock parameter
  name to peak_pixel_rate in header file.
- Add handling for throughput mode 0 granular delta, defined by DP
  Standard v2.1a.
v4:
- Remove the default switch case in
  drm_dp_dsc_sink_max_slice_throughput(), which is unreachable in the
  current code. (Ville)

Cc: dri-devel@lists.freedesktop.org
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reported-and-tested-by: Swati Sharma <swati2.sharma@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250930182450.563016-3-imre.deak@intel.com