Input: i8042 - enable wakeup on a stable struct device

We don't know when the device will be added with device_add() in
serio_add_port() because serio_add_port() is called from a workqueue
that this driver schedules by calling serio_register_port(). The best we
can know is that the device will definitely not have been added yet when
the start callback is called on the serio device.

While it hasn't been shown to be a problem, proactively move the wakeup
enabling calls to the start hook so that we don't race with the
workqueue calling device_add(). This will avoid racy situations where
code tries to add wakeup sysfs attributes for this device from
dpm_sysfs_add() but the path in device_set_wakeup_capable() has already
done so.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>