spapr: CAS and reset cleanup preliminaries PAPR defines a feature negotiation protocol between host and guest called ibm,client-architecture-support or CAS. When invoked by the guest this can either result in updated device tree information being given to the guest to indicate the new configuration, or it can trigger a reboot (called a CAS reboot) for more wide reaching configuration changes. CAS changes are time consuming and irritating for the user, so we'd like to avoid them as much as possible. We hope we can avoid them in all situations, in fact, but there's some work to do to get there. This series has some initial changes that get us closer to that mark.