brcm47xx: fix switch port mapping on Asus RT-N12 and RT-N16 models

On Asus RT-N12 and RT-N16 models, the WAN and LAN4 ports are swapped in the
initial switch configuration since the presets present in nvram appear to be
wrong.

Add special casing for these models to detect_by_model() in order to ensure
a proper switch configuration.

Fixes FS#502.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

target/linux/brcm47xx/base-files/etc/board.d/01_detect

@@ -144,6 +144,8 @@ detect_by_model() {
 		ucidef_set_interfaces_lan_wan "eth0" "eth1"
 		;;
 
+	"Asus RT-N12"* | \
+	"Asus RT-N16"* | \
 	"Asus WL500GP V2" | \
 	"Buffalo WHR-G125" | \
 	"Motorola WR850G" | \