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().

Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>