pinctrl: stm32: drop wrappers around pinctrl_gpio_free/input()

pinctrl_gpio_*() helpers now have signatures corresponding with those of
the GPIOLIB callbacks. We can drop the wrappers.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>