lantiq: fritz7312: set maximum speed to 100 mbit on 5.4

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.

The previous patch in 36f628910b was only applied to the 4.19 file,
so let's just make it consistent with this patch.

Cc: Alexander Couzens <lynxis@fe80.eu>
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/lantiq/files-5.4/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>;
 		};
 	};
 };