ram: rockchip: Add rv1126 ddr4 support

Add support for ddr4 on rv1126. Timing detection files are imported
from downstream Rockchip BSP u-boot. Allow selecting ddr4 ram with
define CONFIG_RAM_ROCKCHIP_DDR4.

Signed-off-by: Tim Lunn <tim@feathertop.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
8 files changed