ramips: fix switch port order for TP-Link Archer C20i

Physical port order watched from the backside of the C20i
(from left to right) is: Internet / 1 / 2 / 3 / 4

Physical Port	Switch port
WAN             0
LAN 3           1
LAN 4           2
LAN 1           3
LAN 2           4
(not used)      5
CPU             6

Signed-off-by: Walter Sonius <walterav1984@gmail.com>
[commit message/title improvements; backport to 19.07]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit a065cd29bf2dfd1ce1f07becd65aef96cec658e7)

target/linux/ramips/base-files/etc/board.d/02_network

@@ -227,7 +227,6 @@ ramips_setup_interfaces()
 	awm002-evb-4M|\
 	awm002-evb-8M|\
 	bdcom,wap2100-sk|\
-	c20i|\
 	dir-645|\
 	gl-mt300a|\
 	gl-mt300n|\
@@ -263,6 +262,7 @@ ramips_setup_interfaces()
 		ucidef_add_switch "switch0" \
 			"1:lan" "2:lan" "3:lan" "4:lan" "0:wan" "6@eth0"
 		;;
+	c20i|\
 	c50|\
 	tplink,c20-v1)
 		ucidef_add_switch "switch0" \