drm/xe: Add for_each_tile iterator

drm/xe: Add for_each_tile iterator

As we start splitting tile handling out from GT handling, we'll need to
be able to iterate over tiles separately from GTs.  This iterator will
be used in upcoming patches.

v2:
 - s/(id__++)/(id__)++/  (Gustavo)

Cc: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://lore.kernel.org/r/20230601215244.678611-6-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>