linux-phytec-fsl

gpio: stmpe: use gpiochip data pointer

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: Bhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>