drm/xe: Move migration from GT to tile

drm/xe: Move migration from GT to tile

Migration primarily focuses on the memory associated with a tile, so it
makes more sense to track this at the tile level (especially since the
driver was already skipping migration operations on media GTs).

Note that the blitter engine used to perform the migration always lives
in the tile's primary GT today.  In theory that could change if media
GTs ever start including blitter engines in the future, but we can
extend the design if/when that happens in the future.

v2:
 - Fix kunit test build
 - Kerneldoc parameter name update
v3:
 - Removed leftover prototype for removed function.  (Gustavo)
 - Remove unrelated / unwanted error handling change.  (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/20230601215244.678611-15-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>