gpiolib: Get rid of not used of_node member

All new drivers should use fwnode and / or parent to provide the
necessary information to the GPIO library.

Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>