Rockchip SoCs have similar boot process, prefer to use TPL for DRAM
init and back to bootrom, and SPL as Trust ATF/U-Boot loader. TPL
common board is a basic TPL board init which can be shared for most
of SoCs to avoid copy-pase for different SoCs.
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
