linux-phytec-fsl

gpio: ath79: use gpiochip data pointer

This makes the driver use the data pointer added to the gpio_chip
to store a pointer to the state container instead of relying on
container_of().

Acked-by: Alban Bedel <albeu@free.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>