ARM: dts: sun7i: bananapi-m1-plus: Enable RGMII RX/TX delay on Ethernet PHY

The Ethernet PHY on the Bananapi M1+ 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 bbc4d71d6354 ("net: phy: realtek: fix rtl8211e
rx/tx delay config").

Fixes: 04c85ecad32a ("ARM: dts: sun7i: Add dts file for Bananapi M1 Plus board")
Signed-off-by: Chen-Yu Tsai <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>
Acked-by: Jernej Skrabec <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm/boot/dts/sun7i-a20-bananapi-m1-plus.dts

···
 	pinctrl-names = "default";
 	pinctrl-0 = <&gmac_rgmii_pins>;
 	phy-handle = <&phy1>;
-	phy-mode = "rgmii";
+	phy-mode = "rgmii-id";
 	phy-supply = <&reg_gmac_3v3>;
 	status = "okay";
 };