rockchip: rk3288: Remove phy reset GPIO pull up

We should not handle this pin explicitly from pinctrl. GMAC driver takes
care of it by using a "reset-gpio" in the DT.

This commit removes pull up for GPIO4B0.

Fixes: 2454b719 ("rockchip: rk3288: Add pinctrl support for the...")
Signed-off-by: Romain Perier <romain.perier@collabora.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>