memory: omap-gpmc: use the dedicated define for GPIO direction

We have a constant defined for this purpose in the gpio/driver.h header
so use it instead of a magic value.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20250407-gpiochip-set-rv-memory-v1-1-5ab0282a9da7@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>