ramips: add support for VoCore2

This patch adds support for the VoCore VoCore2 and its complementary
"ultimate" dock.

Specifications:
- SoC: MediaTek MT7628AN (580MHz, ramips)
- RAM: 128MB DDR2 166MHz
- Storage: 16MB NOR SPI flash onboard + microSD slot on dock
- Wireless: Built into MT7628AN (mt76) with 1T1R firmware on VoCore2
            boards with onboard 1x chip antenna
- Ethernet: 1x100M (port0) on dock, 1x100M (port2) on PCB header
- Dock hardware:
  - USB 2.0 socket
  - MicroSD socket
  - 100Mbps Ethernet x1
  - 3.5mm headphone jack (TRRS) connected to Everest Semi ES8388 I2S
    DAC/ADC (support WIP)
  - Micro USB for power and console (UART2)

Initial installation:
- VoCore2 comes preinstalled with a fork of OpenWrt CC and AP on
  SSID "VoCore2"
- Connect to VoCore2 by Ethernet or Wi-Fi
- `ssh root@192.168.1.1` (password is "vocore")
- scp/wget/etc. LEDE sysupgrade.bin to VoCore2
- `sysupgrade -n <your image>.bin` (don't keep old config, as the
  original firmware uses Ralink SDK Wi-Fi drivers and not
  mt76+mac80211)
- after sysupgrade completes, Wi-Fi will be disabled by default so use
  Ethernet or the micro USB console to configure Wi-Fi again

Signed-off-by: Andrew Yong <me@ndoo.sg>

target/linux/ramips/base-files/etc/board.d/01_leds

@@ -311,6 +311,9 @@ vocore)
 	ucidef_set_led_netdev "eth" "ETH" "$board:orange:eth" "eth0"
 	set_wifi_led "$board:green:status"
 	;;
+vocore2)
+	set_wifi_led "$board:fuchsia:status"
+	;;
 w502u)
 	set_usb_led "$board:blue:usb"
 	set_wifi_led "rt2800pci-phy0::radio"

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

@@ -249,6 +249,10 @@ ramips_setup_interfaces()
 		ucidef_add_switch "switch0" \
 			"1:lan" "2:lan" "3:lan" "4:lan" "5:wan" "0@eth0"
 		;;
+	vocore2)
+		ucidef_add_switch "switch0" \
+			"0:lan" "2:lan" "6t@eth0"
+		;;
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 	v11st-fe|\