smp-core-2020-03-30

  - Support for locked CSD objects in smp_call_function_single_async()
    which allows to simplify callsites in the scheduler core and MIPS

  - Treewide consolidation of CPU hotplug functions which ensures the
    consistency between the sysfs interface and kernel state. The low level
    functions cpu_up/down() are now confined to the core code and not
    longer accessible from random code.