gpio: altera-a10sr: Set gpio_chip parent property

Set the gpio_chip parent property since some recent functions
such as devprop_gpiochip_set_names() can use it.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>