nir/lower_goto_if: Use util/list instead of exec_list

I'm trying to reduce exec_list usage in NIR.  Also, util_list has some
better helpers for a bunch of the operations this pass needs.

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2401>
1 file changed