arm64: rockchip: pinctrl: Do not rely on the node name

Node names for gpio bank were made generic in Linux 5.16 so stop
using them to map the gpio controller to the pin controller bank unit.

Sponsored by: Beckhoff Automation GmbH & Co. KG

(cherry picked from commit 8d6b3a85701062ee795a5aeabb0771c93a8f6f72)