arm64: dts: allwinner: a64: bananapi-m64: Enable RGMII RX/TX delay on PHY

The Ethernet PHY on the Bananapi M64 has the RX and TX delays
enabled on the PHY, using pull-ups on the RXDLY and TXDLY pins.

Fix the phy-mode description to correct reflect this so that the
implementation doesn't reconfigure the delays incorrectly. This
happened with commit bbc4d71d ("net: phy: realtek: fix rtl8211e
rx/tx delay config").

Fixes: e7295499 ("arm64: allwinner: bananapi-m64: Enable dwmac-sun8i")
Fixes: 94f44288 ("arm64: dts: allwinner: A64: Restore EMAC changes")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Acked-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://lore.kernel.org/r/20201024162515.30032-10-wens@kernel.org

arch/arm64/boot/dts/allwinner/sun50i-a64-bananapi-m64.dts

@@ -105,7 +105,7 @@ &ehci1 {
 &emac {
 	pinctrl-names = "default";
 	pinctrl-0 = <&rgmii_pins>;
-	phy-mode = "rgmii";
+	phy-mode = "rgmii-id";
 	phy-handle = <&ext_rgmii_phy>;
 	phy-supply = <&reg_dc1sw>;
 	status = "okay";