lantiq/fritz 7312: set maximum speed to 100 mbit

The fritz 7312 does not support 1000 gbit. Advertising it makes it
worse. Some NIC will change to 1000 gibt and turn off and on again for
ever.

Signed-off-by: Alexander Couzens <lynxis@fe80.eu>

target/linux/lantiq/files-4.19/arch/mips/boot/dts/lantiq/ar9_avm_fritz7312.dts

@@ -108,6 +108,7 @@
 		phy0: ethernet-phy@0 {
 			reg = <0>;
 			reset-gpios = <&gpio 34 GPIO_ACTIVE_LOW>;
+			max-speed = <100>;
 		};
 	};
 };