arm64: rockchip: Add new interface for rk_pinctrl

The gpio controller in rockchips SoC in a child of the pinctrl driver
and cannot control pullups and pulldowns.
Use the new fdt_pinctrl interface for accessing pin capabilities and
setting them.
We can now report that every pins is capable of being IN or OUT function
and PULLUP PULLDOWN.
If the pin isn't in gpio mode no changes will be allowed.

Reviewed by: ganbold (previous version)
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D22849