ram: rockchip: Add initial Kconfig

ram: rockchip: Add initial Kconfig

Right now sdram drivers in rockchip SoC are built based
on the SoC configs which may not be an adequate solutions
while adding common or debug driver.

So, add meaningful Kconfig options start with rk3399.

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