m68k: coldfire: use gpiolib

Force use of gpiolib for Coldfire, as a step towards the deprecation of
GENERIC_GPIO.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Greg Ungerer <gerg@uclinux.org>