drm/xe/pf: Create separate debugfs tree for SR-IOV files

drm/xe/pf: Create separate debugfs tree for SR-IOV files

Currently we expose debugfs files related to SR-IOV functions
together with other native files, but that approach will not
scale well as we plan to add more attributes and also expose
some of them on the per-tile basis.

Start building separate tree for SR-IOV specific debugfs files
where we can replicate similar files per every SR-IOV function:

   /sys/kernel/debug/dri/BDF/
   ├── sriov
   │   ├── pf
   │   │   ├── tile0
   │   │   │   ├── gt0
   │   │   │   ├── gt1
   │   │   │   :
   │   │   ├── tile1
   │   │   :
   │   ├── vf1
   │   │   ├── tile0
   │   │   │   ├── gt0
   │   │   │   ├── gt1
   │   │   │   :
   │   │   :
   │   ├── vf2
   │   ├── ...

We will populate this new tree in upcoming patches.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250928140029.198847-3-michal.wajdeczko@intel.com