gpio: davinci: Add irq chip flag to skip set wake

Add the IRQCHIP_SKIP_SET_WAKE flag since there are no special IRQ Wake
bits that can be set to enable wakeup IRQ.

Fixes: 3d9edf09 ("[ARM] 4457/2: davinci: GPIO support")
Signed-off-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>