radv: Disallow indirect outputs for GS on GFX9 as well.
Since it also uses the output vector before writing to memory. Fixes: e38685cc 'Revert "radv: disable support for VEGA for now."' Reviewed-by:Dave Airlie <airlied@redhat.com> Reviewed-by:
Timothy Arceri <tarceri@itsqueeze.com>