radeonsi: determine correctly if switching from normal launch to fast launch

Fixes: 3da91b3327f - radeonsi/ngg: add VGT_FLUSH when enabling fast launch

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7542>
(cherry picked from commit e29e41a3cd84702a7ea6874f314fca897ca76983)
2 files changed