gpio: move GPIOD flags outside #ifdef

The GPIOD flags are defined inside the #ifdef CONFIG_GPIOLIB
switch, making the gpiolib stubs fail if these flags are used
by a consumer. This is not correct: the stubs should compile
fine without GPIOLIB.

Reported-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>