rockchip: rk3399-evb: defconfig: Enable FDT for new pinctrl driver

The FDT is requested for new pinctrl driver, disable SPL_OF_PLATDATA
to make FDT be built in.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>