gpiolib: add gpio_device_get_base() stub for !GPIOLIB

Add empty stub of gpio_device_get_base() when GPIOLIB is not enabled.

Cc: <stable@vger.kernel.org>
Fixes: 8c85a102 ("gpiolib: provide gpio_device_get_base()")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>