gpio: max77620: Don't set of_node

gpio: max77620: Don't set of_node

The gpiochip_add_data() takes care of setting the of_node to the parent's
device of_node, hence there is no need to do it manually in the driver's
code. This patch corrects the parent's device pointer and removes the
unnecessary setting of the of_node.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Link: https://lore.kernel.org/r/20200709171203.12950-4-digetx@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>