arm64: dts: rockchip: add isp1 node on rk3399

ISP1 is supplied by the tx1rx1 dphy, that is controlled from
inside the dsi1 controller, so include the necessary phy-link
for it.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Tested-by: Sebastian Fricke <sebastian.fricke@posteo.net>
Acked-by: Helen Koike <helen.koike@collabora.com>
Link: https://lore.kernel.org/r/20210210111020.2476369-7-heiko@sntech.de


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