rockchip: io-domain: Add support for RK3399

Port the RK3399 part of the Rockchip IO-domain driver from linux.

This differs from linux version in that pmu io iodomain bit is enabled
in the write ops instead of in an init ops as in linux, this way we can
avoid keeping a full state of all supply that have been configured.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>