drm/xe: Rename pte/pde encoding functions

Remove the leftover TODO by renameing the functions to use xe prefix.
Since the static __gen8_pte_encode() already has a double score,
just remove the prefix.

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20230611222447.2837573-1-lucas.demarchi@intel.com


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