drm/xe: fix has_llc on rkl

Matches i915. Assumption going forward is that non-llc + igpu is only a
thing on MTL+ which should have explicit coherency pat_index settings
for COH_NONE, 1WAY and 2WAY.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Pallavi Mishra <pallavi.mishra@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Pallavi Mishra <pallavi.mishra@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>