ARM: dts: gemini: ns2502: permit to use gigabit

I believed that gigabit was not working due to some unknown missing GPIO.
In fact, gigabit worked when REALTEK_PHY was compiled out.
So the problem was due to PHY delay and we need to use rgmii-id.

Signed-off-by: Corentin Labbe <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

arch/arm/boot/dts/gemini-ns2502.dts

···
 		phy0: ethernet-phy@1 {
 			reg = <1>;
 			device_type = "ethernet-phy";
-			/* We lack the knowledge of necessary GPIO to achieve
-			 * Gigabit
-			 */
-			max-speed = <100>;
 		};
 	};
 };
···
 &ethernet {
 	status = "okay";
 	ethernet-port@0 {
-		phy-mode = "rgmii";
+		phy-mode = "rgmii-id";
 		phy-handle = <&phy0>;
 	};
 };