From: Anton Blanchard <anton@samba.org>

From: Rusty Russell <rusty@rustcorp.com.au>

When hotplug cpu isn't enabled, cpu_is_offline is always false.  I had a stuck
cpu at boot that resulted in a lockup because we tried to start a migration
thread on it.  Instead of cpu_is_offline we can use !cpu_online which should
cover both the hotplug cpu enabled and disabled cases.