rockchip: rk3588: add constants for some register address spaces

It's one thing to have the register mapped via a well-defined struct but
it's another to be able to make use of it. For that to happen, one needs
to cast the physical address memory of the beginning of the register
address space with the struct. Since this cannot change, let's hardcode
it in the include files so that users do not need to duplicate this line
of code in their own implementation.

Cc: Quentin Schulz <foss+uboot@0leil.net>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>