gpio: mockup: don't depend twice on GPIOLIB

config GPIO_MOCKUP is defined in a big if GPIOLIB ... endif block so it
doesn't need to depend explicitly on GPIOLIB.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Link: https://lore.kernel.org/r/20190725131002.14597-1-uwe@kleine-koenig.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>