gpio: mockup: coding-style fix

The indentation is wrong in gpio_mockup_apply_pull(). This patch makes
the code more readable.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20200210155059.29609-1-brgl@bgdev.plSigned-off-by: Linus Walleij <linus.walleij@linaro.org>