m68k: coldfire: Include the GPIO driver header

The Coldfire GPIO driver needs to explicitly incldue the
GPIO driver header since it is providing a driver.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>