arm64: dts: rockchip: disable display subsystem for Lunzn Fastrhino R6xS

The R66S and R68S boards do not have HDMI output, so disable
the display subsystem.

Fixes: c79dab40 ("arm64: dts: rockchip: Add Lunzn Fastrhino R66S")
Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://lore.kernel.org/r/20240701143028.1203997-3-amadeus@jmu.edu.cn


Signed-off-by: Heiko Stuebner <heiko@sntech.de>