arm64: dts: rockchip: add missing address and size cells for rk3399 mipi dsi

DSI controllers are also the hosts of their dsi bus and therefore contain
nodes describing the attached panels with their reg properties containing
the virtual ids.

The dsi controller nodes on rk3399 lacked the #address-cells and #size-cells
for these subnodes, so add them.

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