drm/xe: Add counter for invalid prefetch pagefaults

drm/xe: Add counter for invalid prefetch pagefaults

Add a stats counter for invalid prefetch page faults to avoid
excessive logging.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Varun Gupta <varun.gupta@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260223061906.1420883-2-varun.gupta@intel.com