arm64: dts: rockchip: Add nanopi4 ethernet phy

The nanopi4 boards have the INTB pin of the RTL8211E phy wired up, so we
can make use of that and avoid having to poll for line status changes.
Apparently RTL8211E only requires 30ms of post-reset delay, so we may as
well save a little bit of time there as well.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>