ram: rockchip: Add common ddr type configs

We have common ddr types in rockchip or in general. So use
the common ddr type names instead of per Rockchip SoC to
avoid confusion.

The respective ddr type names will use on the associated
ddr SoC driver as these drivers are built per SoC at a time.

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