drm/xe/pf: Expose PF monitor details via debugfs

For debug purposes we might want to view statistics maintained by
the PF driver about VFs activity.

Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240514190015.2172-9-michal.wajdeczko@intel.com