ar71xx: add support for the Airtight C-60

This patch adds support for the Airtight C-60.

SOC:	Atheros AR9344 rev 2 (CPU:560.000MHz)
RAM:	128 MiB
NOR:	MX25L3205D 4MiB
NAND:	ST Micro NAND 32MiB 3,3V 8-bit
SW-NET:	AR8327N (2 Ports)
WLAN1:	Dual-Band AR9340 Rev:2 (built-in SoC)
WLAN2:	Dual-Band AR9300 Rev:4 PCIe Chip

The switch is setup for an accesspoint:
	LAN1: (gigabit) is the wan-port.
	LAN2: (fast ethernet) is bridged with the br-lan.

Flashing Guide (via initramfs):
  1. Connect a PC to the serial port of the C-60.
     power up the C-60.

     Enter u-boot command prompt:
     #> nand erase
     #> setenv bootcmd "bootm 0x9f060000"
     #> saveenv
     #> setenv ipaddr 192.168.1.1
     #> setenv netmask 255.255.255.0
     #> setenv serverip 192.168.1.100
     #> setenv bootfile lede-ar71xx-nand-c-60-initramfs-kernel.bin
     #> tftpboot
     #> bootm

  2. Wait for the C-60 to boot LEDE.
     On the root prompt. Enter:
     # ubiformat /dev/mtd4
     # ubiattach -p /dev/mtd4

  3. After that copy the sysupgrade.tar onto the router and run:
     # sysupgrade sysupgrade.tar

     to flash the image.

Special thanks to Chris Blake <chrisrblake93@gmail.com>. He provided
a C-60 unit and he helped with debugging the switch, LEDs and platfrom
support.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

target/linux/ar71xx/base-files/lib/upgrade/platform.sh

@@ -424,6 +424,14 @@ platform_check_image() {
 	tew-673gru)
 		dir825b_check_image "$1" && return 0
 		;;
+	c-60|\
+	nbg6716|\
+	r6100|\
+	wndr3700v4|\
+	wndr4300)
+		nand_do_platform_check $board $1
+		return $?
+		;;
 	cpe210|\
 	cpe510)
 		tplink_pharos_check_image "$1" && return 0
@@ -485,13 +493,6 @@ platform_check_image() {
 
 		return 0
 		;;
-	nbg6716|\
-	r6100|\
-	wndr3700v4|\
-	wndr4300)
-		nand_do_platform_check $board $1
-		return $?
-		;;
 	tube2h)
 		alfa_check_image "$1" && return 0
 		return 1
@@ -537,16 +538,17 @@ platform_pre_upgrade() {
 	local board=$(ar71xx_board_name)
 
 	case "$board" in
-	mr18|\
-	z1)
-		merakinand_do_upgrade "$1"
-		;;
+	c-60|\
 	nbg6716|\
 	r6100|\
 	wndr3700v4|\
 	wndr4300)
 		nand_do_upgrade "$1"
 		;;
+	mr18|\
+	z1)
+		merakinand_do_upgrade "$1"
+		;;
 	esac
 }