ar71xx: add support for COMFAST CF-E355AC v2

COMFAST CF-E355AC v2 is a ceiling mount AP with PoE support, based on
Qualcomm/Atheros QCA9531 + QCA9886.

Short specification:

- 2x 10/100 Mbps Ethernet, with PoE support
- 128MB of RAM (DDR2)
- 16 MB of FLASH
- 2T2R 2.4 GHz, 802.11b/g/n
- 2T2R 5 GHz, 802.11ac/n/a, WAVE 2
- built-in 4x 3 dBi antennas
- output power (max): 500 mW (27 dBm)
- 1x RGB LED, 1x button
- built-in watchdog chipset

Flash instruction:

Original firmware is based on OpenWrt.
Use sysupgrade image directly in vendor GUI.

Signed-off-by: Ding Tengfei <dtf@comfast.cn>
[updated kernel config for both boards]
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

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

@@ -216,6 +216,11 @@ cf-e375ac)
 	ucidef_set_led_wlan "wlan1" "WLAN" "comfast:blue:wlan" "phy1tpt"
 	;;
 cf-e355ac|\
+cf-e355ac-v2)
+	ucidef_set_led_netdev "lan" "LAN" "cf-e355ac:green:lan" "eth0"
+	ucidef_set_led_wlan "wlan2g" "WLAN2G" "cf-e355ac:blue:wlan2g" "phy1tpt"
+	ucidef_set_led_wlan "wlan5g" "WLAN5G" "cf-e355ac:red:wlan5g" "phy0tpt"
+	;;
 cf-e380ac-v1|\
 cf-e380ac-v2)
 	ucidef_set_led_netdev "lan" "LAN" "$board:green:lan" "eth0"

target/linux/ar71xx/base-files/etc/hotplug.d/firmware/11-ath10k-caldata

@@ -155,6 +155,7 @@ case "$FIRMWARE" in
 	archer-c58-v1|\
 	archer-c59-v1|\
 	archer-c60-v1|\
+	cf-e355ac-v2|\
 	cf-e375ac)
 		ath10kcal_extract "art" 20480 12064
 		ln -sf /lib/firmware/ath10k/pre-cal-pci-0000\:00\:00.0.bin \