gpio: pca953x: Add wake-up support

Implement the irq_set_wake() method in the (optional) irq_chip of the
GPIO expander, and propagate wake-up settings to the upstream interrupt
controller.  This allows GPIOs connected to a PCA953X GPIO expander to
serve as wake-up sources.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>