drm/xe: Drop extra_gts[] declarations and XE_GT_TYPE_REMOTE

drm/xe: Drop extra_gts[] declarations and XE_GT_TYPE_REMOTE

Now that tiles and GTs are handled separately, extra_gts[] doesn't
really provide any useful information that we can't just infer directly.
The primary GT of the root tile and of the remote tiles behave the same
way and don't need independent handling.

When we re-add support for media GTs in a future patch, the presence of
media can be determined from MEDIA_VER() (i.e., >= 13) and media's GSI
offset handling is expected to remain constant for all forseeable future
platforms, so it won't need to be provided in a definition structure
either.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20230601215244.678611-18-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>