ar71xx: add support for Rockeetech AP531B0

Specification:
- SoC: Qualcomm Atheros QCA9531 (650/400/216 MHz (CPU/DDR/AHB))
- RAM: 64 MiB DDR2
- Storage: 16 MiB of flash (optional 16 MiB second flash)
- Wireless: built into QCA9531 (Honey Bee), PHY modes b/g/n
- Ethernet: 1x100M (port0) 1x100M (port 4)
- PCI-E: x1
- SIMcard slot: x1
- USB 2.0 port: x1 (optional)
- Ext GPIO pin: x8
- UART for serial console: x1
- External watchdog: x1 (optional)
- Power supply: 9-48V (DC jack/passive PoE)

Installation through tftp:
- Copy <Firmware Image Name> into tftp directory
- Connect board via ttl port and Ethernet port
- Boot the AP531B0
- When "Autobooting in 1 seconds" appears press Enter
- Set serverip and ipaddr appropriate
  (e.g. setenv serverip 192.168.88.10;setenv ipaddr 192.168.88.1)
- Enter "tftp 0x8050000 <Firmware Image Name>"
- Enter "erase 0x9f050000 +$filesize"
- Enter "cp.b 0x80500000 0x9f050000 $filesize"
- Enter "reset"

Signed-off-by: Shuanglin Liu <roboidler@gmail.com>

target/linux/ar71xx/base-files/etc/board.d/01_leds

@@ -49,6 +49,11 @@ antrouter-r1)
 	ucidef_set_led_wlan "wlan" "WLAN" "$board:green:wlan" "phy0tpt"
 	ucidef_set_led_default "btc" "BTC" "$board:green:btc" "0"
 	;;
+ap531b0|\
+sc1750|\
+sc450)
+	ucidef_set_led_wlan "wlan" "WLAN" "$board:green:wlan" "phy0tpt"
+	;;
 archer-c59-v1|\
 archer-c60-v1)
 	ucidef_set_led_switch "lan" "LAN" "$board:green:lan" "switch0" "0x1E"
@@ -490,10 +495,6 @@ re450)
 	ucidef_set_led_wlan "wlan2g" "WLAN 2.4 GHz" "$board:blue:wlan2g" "phy1tpt"
 	ucidef_set_led_wlan "wlan5g" "WLAN 5 GHz" "$board:blue:wlan5g" "phy0tpt"
 	;;
-sc1750|\
-sc450)
-	ucidef_set_led_wlan "wlan" "WLAN" "$board:green:wlan" "phy0tpt"
-	;;
 smart-300)
 	ucidef_set_led_netdev "wan" "WAN" "nc-link:green:wan" "eth0"
 	ucidef_set_led_switch "lan1" "LAN1" "nc-link:green:lan1" "switch0" "0x04"

target/linux/ar71xx/base-files/etc/diag.sh

@@ -31,6 +31,7 @@ get_status_led() {
 		status_led="$board:green:system"
 		;;
 	ap132|\
+	ap531b0|\
 	db120|\
 	dr344|\
 	tew-632brp|\