drm/xe: Add backpointer from gt to tile

Rather than a backpointer to the xe_device, a GT should have a
backpointer to its tile (which can then be used to lookup the device if
necessary).

The gt_to_xe() helper macro (which moves from xe_gt.h to xe_gt_types.h)
can and should still be used to jump directly from an xe_gt to
xe_device.

v2:
 - Fix kunit test build
 - Move a couple changes to the previous patch. (Lucas)

Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20230601215244.678611-4-matthew.d.roper@intel.com


Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>