rockchip: arm64: rk3399: add ddr controller driver

RK3399 support DDR3, LPDDR3, DDR4 sdram, this patch is porting from
coreboot, support 4GB lpddr3 in this version.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Added rockchip: tag:
Signed-off-by: Simon Glass <sjg@chromium.org>
6 files changed