drm/xe: Use vfunc to initialize PAT

Split the PAT initialization between SW-only and HW. The _early() only
sets up the ops and data structure that are used later to program the
tables. This allows the PAT to be easily extended to other platforms.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230927193902.2849159-6-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>