rockchip: gru: Set up SoC IO domain registers

The RK3399 SoC needs to know the voltage value provided by some
regulators, which is done by setting relevant register bits. Configure
these the way other RK3399 boards do, but with the same values as are
set in the equivalent code in coreboot.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>