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: Nicolas Saenz Julienne <nicolassaenzj@gmail.com>
Cc: Margarita Olaya <magi@slimlogic.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>