ACPI: EC: Dispatch the EC GPE directly on s2idle wake

On platforms where the Low Power S0 Idle _DSM interface is used,
on wakeup from suspend-to-idle, when it is known that the ACPI SCI
has triggered while suspended, dispatch the EC GPE in order to catch
all EC events that may have triggered the wakeup before carrying out
the noirq phase of device resume.

That is needed to handle power button wakeup on some platforms where
the EC goes into a low-power mode during suspend-to-idle and while in
that mode it will discard events after a timeout.  If that timeout is
shorter than the time it takes to complete the noirq resume of
devices, looking for EC events after the latter is too late.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reported-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Wendy Wang <wendy.wang@intel.com>