dt-bindings: kona-pinctrl: add wakeup interrupt parent for GPIO

Kona SoC has an always-on interrupt controller (PDC) with select GPIO
routed to the PDC as interrupts that can be used to wake the system up
from deep low power modes and suspend.

Change-Id: I562e13682bd6760c3c1a3d9a212d34a4596b4b36
Signed-off-by: Lina Iyer <ilina@codeaurora.org>