drm/i915/dp: Pass DPCD device descriptor to intel_dp_get_dsc_sink_cap()

drm/i915/dp: Pass DPCD device descriptor to intel_dp_get_dsc_sink_cap()

Pass the DPCD sink/branch device descriptor along with the
is_branch/sink flag to intel_dp_get_dsc_sink_cap(). These will be used
by a follow up change to read out the branch device's DSC overall
throughput/line width capabilities and to detect a throughput/link-bpp
quirk.

Reported-and-tested-by: Swati Sharma <swati2.sharma@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250930182450.563016-5-imre.deak@intel.com