ARM: s3c/gpio: complete the conversion to new GPIO value setters

Commit fb52f322 ("ARM: s3c/gpio: use new line value setter
callbacks") correctly changed the assignment of the callback but missed
the check one liner higher. Change it now too to using the recommended
callback as the legacy one is going away soon.

Fixes: fb52f322 ("ARM: s3c/gpio: use new line value setter callbacks")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>