gpio: dln2: fix build breakage

The dln2 driver was initialising a gpiolib private field, which is now
gone.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>