Draft: drm/xe/migrate: Some cleanups and fixes

Some minor fixes and cleanups in migration code.

1. Remove unused 'struct xe_bo *bo' from emit_pte()
2. Use 'false' for is_vram of emit_pte() where it is obvious
3. Pass source bo as 'bo' in xe_migrate_copy() calls
4. Kernel-doc fix for function xe_migrate_clear()
5. In write_pgtable(), consider 'ofs' while calculating chunk size
6. Update xe_migrate_doc.h with 32 page table structs (not 48)

Signed-off-by: Niranjana Vishwanathapura niranjana.vishwanathapura@intel.com