drm/xe: Drop vram_id

The VRAM ID is always the tile ID; there's no need to track it
separately within a GT.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20230601215244.678611-17-matthew.d.roper@intel.com


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