linux-phytec-fsl

gpio: of: provide optional of_mm_gpiochip_add_data() function

In the same spirit as we add an optional void *data argument
to the gpiochip_add_data() call, we need this also for
of_mm_gpiochip_add().

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>