While registering serio device for i8042, mark them as wakeup-capable
and check their user space wakeup settings in i8042_pm_suspend() and
i8042_pm_resume() to enable or disable, respectively, their interrupts
to wake up the system.

This makes it possible to use the PC keyboard to wake up the system
from suspend-to-idle, among other things, after writing "enabled" to
the keyboard serio device's power/wakeup sysfs attribute.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>