gpio: tps65912: fix wrong container_of arguments

gpio: tps65912: fix wrong container_of arguments

commit 2f97c20e5f7c3582c7310f65a04465bfb0fd0e85 upstream.

The gpio_chip operations receive a pointer the gpio_chip struct which is
contained in the driver's private struct, yet the container_of call in those
functions point to the mfd struct defined in include/linux/mfd/tps65912.h.

Signed-off-by: Nicolas Saenz Julienne <nicolassaenzj@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>