drm/xe/pat: Determine ATS / PTA programming during early sw init

drm/xe/pat: Determine ATS / PTA programming during early sw init

Decide whether programming of the special ATS and PTA PAT entries is
necessary (and which entries should be programmed) during early software
initialization rather than hardcoding this into the 'program' functions.
Future platforms may want to re-use the same functions but utilize
different special entry values.  Consolidating all of the decisions
into one place keeps things simple.

Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Link: https://lore.kernel.org/r/20250613214751.792066-3-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>