drm/xe: Allow to assign GGTT region to the VF

drm/xe: Allow to assign GGTT region to the VF

VF's drivers can't modify GGTT PTEs except the range explicitly
assigned by the PF driver. To allow hardware enforcement of this
requirement, each GGTT PTE has a field with the VF number that
identifies which VF can modify that particular GGTT PTE entry.

Only PF driver can modify this field and PF driver shall do that
before VF drivers will be loaded. Add function to prepare PTEs.
Since it will be used only by the PF driver, make it available
only for CONFIG_PCI_IOV=y.

Bspec: 45015, 52395
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240415173937.1287-3-michal.wajdeczko@intel.com