drm/xe: Move VRAM from GT to tile

drm/xe: Move VRAM from GT to tile

On platforms with VRAM, the VRAM is associated with the tile, not the
GT.

v2:
 - Unsquash the GGTT handling back into its own patch.
 - Fix kunit test build
v3:
 - Tweak the "FIXME" comment to clarify that this function will be
   completely gone by the end of the series.  (Lucas)
v4:
 - Move a few changes that were supposed to be part of the GGTT patch
   back to that commit.  (Gustavo)
v5:
 - Kerneldoc parameter name fix.

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/20230601215244.678611-11-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>