Instead of requiring a device pointer, add a functions to select
the pinctrl state based on a device node.
The AM33xx cpsw devicetree description has several subdevices with
pinctrl information attached to them. In barebox we do not handle
the subdevices as distinct devices, so the pinctrl is never configured
correctly and the mdio bus subdevice stops working. This patch makes
it possible to configure the pinctrl without having a device.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>