ramips: add support for Fon FON2601

FON2601 is a wireless router.

Specification:
- SoC: Mediatek MT7620A (580MHz)
- RAM: 128 MiB
- ROM: 16 MiB SPI Flash
- Wireless:
   for 11b/g/n (upto 300 Mbps):  MT7620A built-in WMAC
   for 11a/n/ac (upto 867 Mbps): MT7662E
- Ethernet LAN: 1 port, upto 100 Mbps
- Ethernet WAN: 1 port, upto 1000 Mbps
- USB: 1 port (USB 2.0 host)
- LEDs: 4 (all can be controlled by SoC's GPIO)
- buttons: 1 (Displayed as "WPS" on enclosure)
- serial port: 57600n8
 pins: Vcc(3.3V), Rx, Tx, GND
(left to right, viewed from outside of board)

Installation (only available via UART):
  1. download sysupgrade binary image by wget command
  2. write sysupgrade binary image to Flash
     command is:
       mtd write sysupgrade.bin firmware
  3. reboot

Important Notice:
  Only one button is displayed as "WPS" on enclosure.
  However, it is configured as "reset" (factory resetting feature).

Signed-off-by: NOGUCHI Hiroshi <drvlabo@gmail.com>
[removed unrelated openwrt-keyring revert, missing -Wall for uimage_padhdr]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

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

@@ -329,6 +329,10 @@ ramips_setup_interfaces()
 		ucidef_add_switch "switch1" \
 			"1:lan" "2:lan" "3:lan" "4:lan" "0:wan" "6@eth0"
 		;;
+	fon,fon2601)
+		ucidef_add_switch "switch0" \
+			"0:lan" "4:wan" "6@eth0"
+		;;
 	gehua,ghl-r-001)
 		ucidef_add_switch "switch0" \
 			"0:lan" "1:lan" "2:lan" "4:wan" "6@eth0"