cpumask: use set_cpu_active in init/main.c

cpu_active_map is deprecated in favor of cpu_active_mask, which is
const for safety: we use accessors now (set_cpu_active) is we really
want to make a change.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/init/main.c b/init/main.c
index 1ac7ec7..d6b388f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -407,8 +407,7 @@
 	 * Set up the current CPU as possible to migrate to.
 	 * The other ones will be done by cpu_up/cpu_down()
 	 */
-	cpu = smp_processor_id();
-	cpu_set(cpu, cpu_active_map);
+	set_cpu_active(smp_processor_id(), true);
 
 	/* FIXME: This should be done in userspace --RR */
 	for_each_present_cpu(cpu) {