ath79: add support for TP-Link TL-WA830RE v1

This ports support for the TL-WA830RE v1 range extender from ar71xx to
ath79.

Specifications:
- SOC: Atheros AR7240
- CPU: 400MHz
- Flash: 4 MiB (Spansion S25FL032P)
- RAM: 32 MiB (Zentel A3S56D40FTP-G5)
- WLAN: Atheros AR9280 bgn 2x2
- Ethernet: 1 port (100M)

Flash instructions:
- install from u-boot with tftp (requires serial access)
  > setenv ipaddr a.b.c.d
  > setenv serverip e.f.g.h
  > tftpboot 0x80000000 \
      openwrt-ath79-tiny-tplink_tl-wa830re-v1-squashfs-factory.bin
  > erase 0x9f020000 +0x3c0000
  > cp.b 0x80000000 0x9f020000 0x3c0000
  > bootm 0x9f020000
- flash factory image from OEM WebUI
- sysupgrade from ar71xx image

The device seems to be a clone of the following devices not yet
added to ath79:
- tl-wa701nd-v1
- tl-wa730re-v1
- tl-wa801nd-v1
- tl-wa901nd-v1

Signed-off-by: Christian Buschau <christian.buschau@mailbox.org>
[make use of ar7240_tplink.dtsi, add note about clones]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ath79/tiny/base-files/etc/board.d/01_leds

@@ -41,7 +41,8 @@ on,n150r)
 	ucidef_set_led_switch "lan2" "LAN2" "netgear:green:lan2" "switch0" "0x04" "0x0f"
 	;;
 tplink,tl-mr3020-v1|\
-tplink,tl-mr3040-v2)
+tplink,tl-mr3040-v2|\
+tplink,tl-wa830re-v1)
 	ucidef_set_led_netdev "lan" "LAN" "tp-link:green:lan" "eth0"
 	;;
 tplink,tl-mr3420-v2|\

target/linux/ath79/tiny/base-files/etc/board.d/02_network

@@ -32,6 +32,7 @@ ath79_setup_interfaces()
 	tplink,tl-mr10u|\
 	tplink,tl-mr3020-v1|\
 	tplink,tl-mr3040-v2|\
+	tplink,tl-wa830re-v1|\
 	tplink,tl-wa850re-v1|\
 	tplink,tl-wa850re-v2|\
 	tplink,tl-wa901nd-v2|\

target/linux/ath79/tiny/base-files/etc/hotplug.d/firmware/10-ath9k-eeprom

@@ -10,6 +10,7 @@ case "$FIRMWARE" in
 "ath9k-eeprom-pci-0000:00:00.0.bin")
 	case $board in
 	buffalo,whr-g301n|\
+	tplink,tl-wa830re-v1|\
 	tplink,tl-wr841-v5|\
 	tplink,tl-wr941-v4)
 		caldata_extract "art" 0x1000 0xeb8