rockchip: io-domain: add support for PX30

Port the PX30 part of the Rockchip IO Domain driver from Linux.

This differs from linux version in that the 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 supplies that have been configured.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>