drm/xe/bmg: Program an additional discrete-specific PAT setting

Discrete Xe2 platforms require programming of one additional row of PAT
settings which controls the access characteristics for PPGTT and LMTT
page tables.  Integrated GPUs do not need this programming and will
leave the register at its hardware default value.

Bspec:  71582
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240408170545.3769566-6-balasubramani.vivekanandan@intel.com