arm64: dts: rockchip: Disable CDN DP on Pinebook Pro

arm64: dts: rockchip: Disable CDN DP on Pinebook Pro

The CDN DP needs a PHY and a extcon to work correctly. But no extcon is
provided by the device-tree, which leads to an error:
cdn-dp fec00000.dp: [drm:cdn_dp_probe [rockchipdrm]] *ERROR* missing extcon or phy
cdn-dp: probe of fec00000.dp failed with error -22

Disable the CDN DP to make graphic work on the Pinebook Pro.

Reported-by: Guillaume Gardet <guillaume.gardet@arm.com>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Link: https://lore.kernel.org/r/20210715164101.11486-1-matthias.bgg@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>