[U-Boot] rockchip: rk3188: ram: add support for 16bit row address

[Philipp Tomsich]

> RK3188 using the same ddr_conf for both 15 bit and 16 bit row address.
> 
> Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
> ---
> 
>  drivers/ram/rockchip/sdram_rk3188.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>