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: linux-mips@linux-mips.org
Cc: Alban Bedel <albeu@free.fr>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>