drm/xe: xe_engine_create_ioctl should check gt_count, not tile_count

Platforms like MTL only have a single tile, but multiple GTs.
Ensure XE_ENGINE_CREATE accepts engine creation on gt1 on such
platforms.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20230725003433.1992137-4-matthew.d.roper@intel.com


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