powerpc: Call no-longer static setup_nr_cpu_ids instead of replicating it

c1854e00 (powerpc: Set nr_cpu_ids early
and use it to free PACAs) copied the formerly static setup_nr_cpu_ids
from init/main.c but 34db18a0 (smp:
move smp setup functions to kernel/smp.c) moved it to kernel/smp.c
with a declaration in include/linux/smp.h, so we can call it instead of
replicating it.
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/setup-common.c

@@ -510,7 +510,7 @@ void __init smp_setup_cpu_maps(void)
 	cpu_init_thread_core_maps(nthreads);
 
 	/* Now that possible cpus are set, set nr_cpu_ids for later use */
-	nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
+	setup_nr_cpu_ids();
 
 	free_unused_pacas();
 }