acpi_install_notify_handler() could fail.  So check the exit status
and give a better debug info.
Signed-off-by: NTang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>