drm/xe: Move ASID allocation and user PT BO tracking into xe_vm_create

drm/xe: Move ASID allocation and user PT BO tracking into xe_vm_create

Currently, ASID assignment for user VMs and page-table BO accounting for
client memory tracking are performed in xe_vm_create_ioctl.
To consolidate VM object initialization, move this logic to
xe_vm_create.

v2:
 - removed unnecessary duplicate BO tracking code
 - using the local variable xef to verify whether the VM is being created
   by userspace

Suggested-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://lore.kernel.org/r/20250811104358.2064150-3-piotr.piorkowski@intel.com
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>