ramips: add support for ALFA Network AC1200RM

ALFA Network AC1200RM is an AC1200 router, with 5-port FE switch and
USB 2.0 port. Device is based on MediaTek MT7620A + MT7612EN.

Specification:

- MT7620A (580 MHz)
- 64 MB of RAM (DDR2)
- 16 MB of FLASH (SPI NOR)
- 5x 10/100 Mbps Ethernet with passive PoE output in WAN and LAN4
- 2T2R 2.4 GHz (MT7620A)
- 2T2R 5 GHz (MT7612EN)
- 1x USB 2.0
- 9x LED (8 driven by GPIO)
- 1x button (reset)
- DC jack for main power input (12-24 V)
- 2x UART, I2C, I2S and LED headers

Flash instruction (do it under U-Boot, using UART and TFTP server):

Select option "2: Load system code then write to Flash via TFTP" and
use "sysupgrade" image.

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

target/linux/ramips/image/mt7620.mk

@@ -27,6 +27,15 @@ define Device/ai-br100
 endef
 TARGET_DEVICES += ai-br100
 
+define Device/alfa-network_ac1200rm
+  DTS := AC1200RM
+  IMAGE_SIZE := 16064k
+  DEVICE_TITLE := ALFA Network AC1200RM
+  DEVICE_PACKAGES := kmod-usb2 kmod-usb-ohci
+  SUPPORTED_DEVICES := $(subst _,$(comma),$(1))
+endef
+TARGET_DEVICES += alfa-network_ac1200rm
+
 define Device/Archer
   TPLINK_HWREVADD := 0
   TPLINK_HVERSION := 3