gpiolib: use 'unsigned int' instead of 'unsigned' in gpio_set_config()

Checkpatch complains about using 'unsigned' instead of 'unsigned int'.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>