drm/xe: Use FIELD_PREP/FIELD_GET for tile id encoding

Use FIELD_PREP()/FIELD_GET() to encode the tile id into flags. Besides
protecting for eventual overflow it also makes it easier to see a new
flag can't be added as BIT(7).

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20230718193924.3084759-2-lucas.demarchi@intel.com


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