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/image/Makefile

@@ -147,6 +147,11 @@ define Build/sercom-footer
 	$(call Build/sercom-seal,-f)
 endef
 
+define Build/fonfxcimage
+	uimage_padhdr -i $@ -o $@.new
+	mv $@.new $@
+endef
+
 ifeq ($(SUBTARGET),rt288x)
 include rt288x.mk
 endif

target/linux/ramips/image/mt7620.mk

@@ -372,6 +372,19 @@ define Device/elecom_wrh-300cr
 endef
 TARGET_DEVICES += elecom_wrh-300cr
 
+define Device/fon_fon2601
+  MTK_SOC := mt7620a
+  IMAGE_SIZE := 15936k
+  DEVICE_VENDOR := Fon
+  DEVICE_MODEL := FON2601
+  DEVICE_PACKAGES := kmod-mt76x2 kmod-usb2 kmod-usb-ohci
+  KERNEL_INITRAMFS := $$(KERNEL) | fonfxcimage
+  IMAGE/sysupgrade.bin := append-kernel | append-rootfs |\
+			fonfxcimage |\
+			pad-rootfs | append-metadata | check-size $$$$(IMAGE_SIZE)
+endef
+TARGET_DEVICES += fon_fon2601
+
 define Device/glinet_gl-mt300a
   MTK_SOC := mt7620a
   IMAGE_SIZE := 15872k