rockchip: rk3399: Enable DT overlay support on all boards

Imply OF_LIBFDT_OVERLAY Kconfig options to add device tree overlay
support on all RK3399 boards.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
5 files changed