ath79: add support for Buffalo BHR-4GRV

Buffalo BHR-4GRV is a wired router, based on Atheros AR7242.

Specification:

- Atheros AR7242
- 64 MB of RAM
- 32 MB of Flash
  - 2x 16 MB SPI-NOR flash
- 5x 10/100/1000 Mbps Ethernet
- 3x LEDs, 2x keys
- 1x USB 2.0 Type-A
- UART header on PCB
  - JP1: Vcc, GND, TX, RX from reset button side

Flash instruction using factory image:

1. Boot the BHR-4GRV normaly and connect the computer to its LAN port
2. Access to
"http://192.168.11.1/cgi-bin/cgi?req=frm&frm=py-db/firmup.html"
with user "bufpy" and password "otdpopy"
3. Select the OpenWrt factory image and click "OK" button to perform
firmware upgrade
4. Wait ~200 seconds to complete flashing

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>

target/linux/ath79/image/generic.mk

@@ -69,6 +69,19 @@ define Device/avm_fritz4020
 endef
 TARGET_DEVICES += avm_fritz4020
 
+define Device/buffalo_bhr-4grv
+  ATH_SOC := ar7242
+  DEVICE_TITLE := Buffalo BHR-4GRV
+  DEVICE_PACKAGES := kmod-usb-core kmod-usb2 kmod-usb-ledtrig-usbport
+  IMAGE_SIZE := 32256k
+  IMAGES += factory.bin tftp.bin
+  IMAGE/default := append-kernel | pad-to $$$$(BLOCKSIZE) | append-rootfs | pad-rootfs | check-size $$$$(IMAGE_SIZE)
+  IMAGE/factory.bin := $$(IMAGE/default) | buffalo-enc BHR-4GRV 1.99 | buffalo-tag BHR-4GRV
+  IMAGE/tftp.bin := $$(IMAGE/default) | buffalo-tftp-header
+  SUPPORTED_DEVICES += wzr-hp-g450h
+endef
+TARGET_DEVICES += buffalo_bhr-4grv
+
 define Device/buffalo_wzr-hp-ag300h
   ATH_SOC := ar7161
   DEVICE_TITLE := Buffalo WZR-HP-AG300H