drm/xe/pf: Prepare sysfs for SR-IOV admin attributes

drm/xe/pf: Prepare sysfs for SR-IOV admin attributes

We already have some SR-IOV specific knobs exposed as debugfs
files to allow low level tuning of the SR-IOV configurations,
but those files are mainly for the use by the developers and
debugfs might not be available on the production builds.

Start building dedicated sysfs sub-tree under xe device, where
in upcoming patches we will add selected attributes that will
help provision and manage PF and all VFs:

  /sys/bus/pci/drivers/xe/BDF/
  ├── sriov_admin/
      ├── pf/
      ├── vf1/
      ├── vf2/
      :
      └── vfN/

Add all required data types and helper macros that will be used
by upcoming patches to define actual attributes.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patch.msgid.link/20251030222348.186658-2-michal.wajdeczko@intel.com