powerpc: Set nr_cpu_ids early and use it to free PACAs

Without this, "holes" in the CPU numbering can cause us to
free too many PACAs
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/paca.c

@@ -203,7 +203,7 @@ void __init free_unused_pacas(void)
 {
 	int new_size;
 
-	new_size = PAGE_ALIGN(sizeof(struct paca_struct) * num_possible_cpus());
+	new_size = PAGE_ALIGN(sizeof(struct paca_struct) * nr_cpu_ids);
 
 	if (new_size >= paca_size)
 		return;

arch/powerpc/kernel/setup-common.c

@@ -509,6 +509,9 @@ 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;
+
 	free_unused_pacas();
 }
 #endif /* CONFIG_SMP */