In analogy with commits 5af84b8270 and 97df8c1299, using
asynchronous threads can improve the overall suspend_late
time significantly.
This patch is for suspend_late phase.
Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>