Add a minimal generic RK3399 board that only have eMMC, SDMMC, SPI flash
and USB OTG enabled. This defconfig can be used to boot from eMMC,
SD-card or SPI flash on most RK3399 boards that follow reference board
design.
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Christopher Obbard <christopher.obbard@linaro.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
