num_possible_cpus() returns how many CPUs may be present on system.
However we want the highest possible CPU number.
This may be differ in a sparsed possible CPUs map.
Such map achived by OF for plat-eznps.
For example if we have:
possible cpus mask 0,3
Then:
num_possible_cpus() is equal 2
while
nr_cpu_ids is equal 4.
Only for value 4 c_start() will provide correct cpuinfo at procfs.