cpumask: use new cpumask functions throughout x86

Impact: cleanup

1) &cpu_online_map -> cpu_online_mask
2) first_cpu/next_cpu_nr -> cpumask_first/cpumask_next
3) cpu_*_map manipulation -> init_cpu_* / set_cpu_*

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

arch/x86/kernel/process.c

@@ -324,7 +324,7 @@ void stop_this_cpu(void *dummy)
 	/*
 	 * Remove this CPU:
 	 */
-	cpu_clear(smp_processor_id(), cpu_online_map);
+	set_cpu_online(smp_processor_id(), false);
 	disable_local_APIC();
 
 	for (;;) {