drm/xe/svm: Split system allocator vma incase of madvise call

drm/xe/svm: Split system allocator vma incase of madvise call

If the start or end of input address range lies within system allocator
vma split the vma to create new vma's as per input range.

v2 (Matthew Brost)
- Add lockdep_assert_write for vm->lock
- Remove unnecessary page aligned checks
- Add kerrnel-doc and comments
- Remove unnecessary unwind_ops and return

v3
- Fix copying of attributes

v4
- Nit fixes

v5
- Squash identifier for madvise in xe_vma_ops to this patch

v6/v7/v8
- Rebase on drm_gpuvm changes

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250821173104.3030148-6-himal.prasad.ghimiray@intel.com
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>