drm/i915/dp: Add intel_dp_dsc_get_slice_config()

drm/i915/dp: Add intel_dp_dsc_get_slice_config()

Add intel_dp_dsc_get_slice_config() to compute the detailed slice
configuration and determine the slices-per-line value (returned by
intel_dp_dsc_get_slice_count()) using this function.

v2: Fix incorrectly returning false from intel_dp_dsc_min_slice_count()
    due to rebase fail. (Jouni)

Cc: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260114162232.92731-15-imre.deak@intel.com