If chip->to_irq is NULL ACPI GPIO helpers don't register GPIO event
handlers thus preventing any ACPI GPIO triggered events. Solve this by
calling gpiochip_add() after we have set up drivers chip->to_irq hook.
Signed-off-by: NJin Yao <yao.jin@intel.com>
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>