gpio: twl4030: Reorder functions which allows to drop a forward declaraion

There is no cyclic dependency between gpio_twl4030_probe() and
gpio_twl4030_remove(), so by moving the latter before the former the
forward declaration can be dropped.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>