ACPI / osl: implement acpi_os_sleep() with msleep()

Currently, acpi_os_sleep() uses schedule_timeout_interruptible()
which can be interrupted by a signal, and that causes the real sleep
time to be shorter.

According to the ACPI spec:

 The Sleep term is used to implement long-term timing requirements.
 Execution is delayed for at least the required number of milliseconds.

The sleeping time should be at least the required number msecs, so use
msleep() which guarantees that to implement it.

Signed-off-by: Liu Chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>