arm64: dts: rockchip: Add mdio and ethernet-phy nodes to rk3308-rock-pi-s

Be explicit about the Ethernet port and define mdio and ethernet-phy
nodes in the device tree for ROCK Pi S.

Fixes: bc3753ae ("arm64: dts: rockchip: rock-pi-s add more peripherals")
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Link: https://lore.kernel.org/r/20240521211029.1236094-8-jonas@kwiboo.se


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