drm/xe: Remove unused xe_bo_to_tile

Unused and would like to remove the memtype_to_tile() which it calls.

Signed-off-by: Brian Welty <brian.welty@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>