gpio: zynq: use container_of() to get state container
gpio: zynq: use container_of() to get state container

The state container of the Zynq GPIO driver is sometimes
extracted from the gpio_chip exploiting the fact that offsetof()
the struct gpio_chip inside the struct zynq_gpio is 0, so
the container_of() is in practice a noop. However if a member
is added to struct zynq_gpio in front of struct gpio_chip,
things will break. Using proper container_of() avoids this
problem.

Semantically this is a noop, the compiler will optimize it away,
but syntactically it makes me happier.

Also replace some explicit container_of() calls with the helper
function.

Cc: Lars-Peter Clausen <3318dc5ce3e4fb7c28a0b841b6801c884e1d0896@metafoo.de>
Cc: Ezra Savard <7b88235fe39ee3934a49ae2829b3ee81e9d259c3@xilinx.com>
Cc: Michal Simek <b20e59da6aeb5cea6c82b021069d69f63616c55d@xilinx.com>
Acked-by: Harini Katakam <460912b7442082efd17dd2415499351621819deb@xilinx.com>
Signed-off-by: Linus Walleij <9cd9d802d23c0ed5e224beabf4ae4a5c478746ef@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs