arm64: dts: allwinner: Pine H64: Enable both RGMII RX/TX delay

Since commit bbc4d71d ("net: phy: realtek: fix rtl8211e rx/tx delay config"),
the network is unusable on PineH64 model A.

This is due to phy-mode incorrectly set to rgmii instead of rgmii-id.

Fixes: 729e1ffc ("arm64: allwinner: h6: add support for the Ethernet on Pine H64")
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201019063449.33316-1-clabbe@baylibre.com