drm/xe/huc: HuC is not supported on GTs that don't have video engines

On MTL-style multi-gt platforms, the HuC is only available on the media
GT, so we need to consider it as not supported on the render GT.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>