pinctrl: mediatek: fix dual-edge code defect

pinctrl: mediatek: fix dual-edge code defect

commit 5edf673d07fdcb6498be24914f3f38f8d8843199 upstream.

When a dual-edge irq is triggered, an incorrect irq will be reported on
condition that the external signal is not stable and this incorrect irq
has been registered.
Correct the register offset.

Signed-off-by: Hongkun Cao <hongkun.cao@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>