input: keyboard: add syscore_ops support to gpio_key driver

Add syscore_ops support for gpio-keys driver to service
wakeable irq handler before the CPUs resume after
suspend state.

Signed-off-by: Shantanu Jain <shjain@codeaurora.org>
Change-Id: I7fe266661abfd469c68309a66aed0cb0fa2de33e