drm/xe/svm: Make xe_svm_range_needs_migrate_to_vram() public

drm/xe/svm: Make xe_svm_range_needs_migrate_to_vram() public

xe_svm_range_needs_migrate_to_vram() determines whether range needs
migration to vram or not, modify it to accept region preference parameter
too, so we can use it in prefetch too.

v2
- add assert instead of warn (Matthew Brost)

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250513040228.470682-11-himal.prasad.ghimiray@intel.com
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>