void __init setup_cpu_maps ( void);
cpu_possible_map cpu_present_map cpu_sibling_map
Having the possible map set up early allows us to restrict allocations of things like irqstacks to num_possible_cpus rather than NR_CPUS.
We do not initialize the online map here; cpus set their own bits in cpu_online_map as they come up.
This function is valid only for Open Firmware systems. finish_device_tree must be called before using this.
While we're here, we may as well set the ``physical'' cpu ids in the paca.