ar71xx: add support for YunCore CPE870

YunCore CPE870 is an outdoor CPE/AP based on Atheros AR9341.
Short specification:

- 535/400/200 MHz (CPU/DDR/AHB)
- 2x 10/100 Mbps Ethernet, passive PoE support
- 64/128 MB of RAM (DDR2)
- 8 MB of FLASH
- 2T2R 2.4 GHz with external PA (SKY65174-21), up to 30 dBm
- internal 14 dBi panel antenna
- 8x LED, 1x button
- UART (JP1) header on PCB

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

1. tftp 0x80060000 lede-ar71xx-generic-cpe870-squashfs-sysupgrade.bin
2. erase 0x9f020000 +$filesize
3. cp.b $fileaddr 0x9f020000 $filesize
4. setenv bootcmd "bootm 0x9f020000"
5. saveenv && reset

Vendor firmware access (login/password): Admin/5up

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

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

@@ -58,6 +58,7 @@ ap147-010)
 	ucidef_set_led_wlan "wlan2g" "WLAN 2.4 GHz" "ap147:green:wlan-2g" "phy0tpt"
 	;;
 ap90q|\
+cpe870|\
 dr531)
 	ucidef_set_led_netdev "lan" "LAN" "$board:green:lan" "eth0"
 	ucidef_set_led_netdev "wan" "WAN" "$board:green:wan" "eth1"
@@ -66,6 +67,14 @@ dr531)
 	ap90q)
 		ucidef_set_led_wlan "wlan" "WLAN" "$board:green:wlan" "phy0tpt"
 		;;
+	cpe870)
+		ucidef_set_led_wlan "wlan" "WLAN" "$board:green:wlan" "phy0tpt"
+		ucidef_set_rssimon "wlan0" "200000" "1"
+		ucidef_set_led_rssi "rssilow" "RSSILOW" "$board:green:link1" "wlan0" "1" "100" "0" "13"
+		ucidef_set_led_rssi "rssimediumlow" "RSSIMEDIUMLOW" "$board:green:link2" "wlan0" "26" "100" "-25" "13"
+		ucidef_set_led_rssi "rssimediumhigh" "RSSIMEDIUMHIGH" "$board:green:link3" "wlan0" "51" "100" "-50" "13"
+		ucidef_set_led_rssi "rssihigh" "RSSIHIGH" "$board:green:link4" "wlan0" "76" "100" "-75" "13"
+		;;
 	esac
 	;;
 bhr-4grv2)

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

@@ -48,6 +48,7 @@ get_status_led() {
 		status_led="$board:green:power"
 		;;
 	ap90q|\
+	cpe870|\
 	gl-inet)
 		status_led="$board:green:lan"
 		;;