MFC r356148-r356149, r356277

r356148:
arm64: rockchip: rk808: Add remaining regulators

The RK808 driver was missing the LDO and switch regulators.
Add support for them.

Reviewed by: mmel
Differential Revision: https://reviews.freebsd.org/D22852

r356149:
arm64: rockchip: Add driver for the io domain

This driver configure the registers in the GRF according to the value
of the regulators for the platform.
Some IP can run with either 3.0V or 1.8V, if we don't configure them
correctly according to the external voltage used they will not work.
It's only done at boot time for now and might be needed at runtime for
IP like sdmmc.

Reviewed by: mmel
Tested On: RockPro64, Firefly-RK3399 (gonzo), AIO-3288 (mmel)
Differential Revision: https://reviews.freebsd.org/D22854

r356277:
arm64: rockchip: Add a module for rk_spi

The spi node doesn't lives under a simple-bus compatible node so we need
OFWBUS_PNP_INFO instead of SIMPLEBUS_PNP_INFO.