Add a minimal generic RK3566/RK3568 board that only have eMMC and SDMMC
enabled. This defconfig can be used to boot from eMMC or SD-card on most
RK3566/RK3568 boards that follow reference board design.
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
