ram: rockchip: Add debug sdram driver

ram: rockchip: Add debug sdram driver

Add sdram driver to handle debug across rockchip SoCs.

This would help to improve code debugging feature for
sdram drivers in rockchip family, whoever wants to
debug the driver should call these core debug code on
their respective platform sdram drivers.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: YouMin Chen <cym@rock-chips.com>
Reviewed-by: Kever Yang <Kever.yang@rock-chips.com>