drm/xe: Remove vma arg from xe_pte_encode()

All the callers pass a NULL vma, so the buffer is always the BO. Remove
the argument and the side effects of dealing with it.

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20230726160708.3967790-5-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>