drm/xe: Add missing DG2 lrc tunings

drm/xe: Add missing DG2 lrc tunings

Synchronize with i915 the DG2 tunings as of
commit 4d14d7717f19 ("drm/i915/selftest: Fix ktime_get() and h/w access
order").

Contrary to the tuning "gang timer" for TGL, there is no quick
justification for why the read back is disabled in i915. Keep it
with that flag for now. That can be tentatively removed later when the
read values are checked.

v2: Use XEHP_FF_MODE2 instead of GEN12_FF_MODE2 (Matt Roper)

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230314003012.2600353-11-lucas.demarchi@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>