ramips: mt7620/mt7621: remove invalid mediatek,portmap

mt7620 and mt7621 use mt7530 driver, which only accepts "llllw", "wllll",
and "lwlll" values.

According to its switch setup, Mi Router 3G v2 has a WAN port at port 4,
so the correct value should be "llllw".

Signed-off-by: Sungbo Eo <mans0n@gorani.run>
(backported from commit d3c0a944059bb0d45c3b56278249100258378b0c)
[removed devices not in 19.07]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ramips/dts/ArcherMR200.dts

@@ -171,9 +171,8 @@
 };
 
 &ethernet {
-		mtd-mac-address = <&rom 0xf100>;
-		mediatek,portmap = "llll";
-	};
+	mtd-mac-address = <&rom 0xf100>;
+};
 
 &ehci {
 	status = "okay";