drm/xe: Reset VMA attributes to default in SVM garbage collector

Restore default memory attributes for VMAs during garbage collection
if they were modified by madvise. Reuse existing VMA if fully overlapping;
otherwise, allocate a new mirror VMA.

v2 (Matthew Brost)
- Add helper for vma split
- Add retry to get updated vma

v3
- Rebase on gpuvm layer

Suggested-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250821173104.3030148-19-himal.prasad.ghimiray@intel.com


Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>