ramips: fix Archer C20i wireless MAC address

The TP-Link Archer C20i previously had a generic Ralink MAC address set
for both radios, as the caldata does only contain a generic MAC address.

Set the MAC address from the vendor firmware for both radios to assign
unique MAC addresses to every device.

Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/ramips/dts/mt7620a_tplink_archer-c20i.dts

@@ -53,3 +53,12 @@
 		ralink,function = "gpio";
 	};
 };
+
+&wmac {
+	mtd-mac-address = <&rom 0xf100>;
+};
+
+&wifi {
+	mtd-mac-address = <&rom 0xf100>;
+	mtd-mac-address-increment = <(-1)>;
+};