drm/xe: Add xe_vm_pgtable_update_op to xe_vma_ops

Each xe_vma_op resolves to 0-3 pt_ops. Add storage for the pt_ops to
xe_vma_ops which is dynamically allocated based the number and types of
xe_vma_op in the xe_vma_ops list. Allocation only implemented in this
patch.

This will help with converting xe_vma_ops (multiple xe_vma_op) in a
atomic update unit.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240704041652.272920-3-matthew.brost@intel.com