can: mcp251x: mcp251x_gpio_setup(): Get rid of duplicate of_node assignment

can: mcp251x: mcp251x_gpio_setup(): Get rid of duplicate of_node assignment

GPIO library does copy the of_node from the parent device of the GPIO
chip, there is no need to repeat this in the individual drivers.
Remove assignment here.

For the details one may look into the of_gpio_dev_init()
implementation.

Link: https://lore.kernel.org/all/20211202205855.76946-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>