fd_fence_create_unflushed() is called with the driver context, but
fd_fence_finish() is called with the threaded/frontend context, which
is what threaded_context_flush() expects to be passed.
Fixes: c4e5beef07 ("freedreno: threaded_context async flush support")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9627>