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: Daniel Mack <zonque@gmail.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>