lima/gpir: Fix fake dep handling for schedule_first nodes

lima/gpir: Fix fake dep handling for schedule_first nodes

The whole point of schedule_first nodes is that they need to be
scheduled as soon as possible, so if a schedule_first node is the
successor in a fake dependency that prevents it from being scheduled
after its parent, that can cause problems. We need to add these fake
dependencies to the parent as well, and we need to guarantee that the
pre-RA scheduler puts schedule_first nodes right before their parents in
order to prevent this from adding cycles to the dependency graph.

Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Tested-by: Vasily Khoruzhick <anarsoul@gmail.com>