ath79: add support for TP-Link TL-WR740N v5

This adds support for the TP-Link TL-WR740N v5, a clone of the
v4 only with a different TPLINK_HWID. It was already supported
in ar71xx as well.

Specifications:

SOC: Atheros AR9331
CPU: 400MHz
Flash: 4 MiB
RAM: 32 MiB
WLAN: Atheros AR9330 bgn
Ethernet: 5 ports (100M)

Flashing instructions:

- Flash factory image from OEM WebUI:
  openwrt-ath79-tiny-tplink_tl-wr740n-v5-squashfs-factory.bin
- Sysupgrade from ar71xx image:
  openwrt-ath79-tiny-tplink_tl-wr740n-v5-squashfs-sysupgrade.bin

Signed-off-by: Jun Su <howard0su@gmail.com>
[commit title/message facelift, backport for 19.07]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit b9f4f1f97aeeec65a872c4c5b1a0528a69d16d7b)

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

@@ -189,6 +189,7 @@ tplink,tl-wr941-v4)
 	ucidef_set_led_switch "lan4" "LAN4" "tp-link:green:lan4" "switch0" "0x10"
 	;;
 tplink,tl-wr740n-v4|\
+tplink,tl-wr740n-v5|\
 tplink,tl-wr741nd-v4|\
 tplink,tl-wr841-v8|\
 tplink,tl-wr842n-v2)

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

@@ -234,6 +234,7 @@ ath79_setup_interfaces()
 			"1:lan" "2:lan" "3:lan" "4:lan" "0:wan" "9@eth0"
 		;;
 	tplink,tl-wr740n-v4|\
+	tplink,tl-wr740n-v5|\
 	tplink,tl-wr741nd-v4|\
 	tplink,tl-wr841-v8|\
 	tplink,tl-wr842n-v2)

target/linux/ath79/dts/ar9331_tplink_tl-wr740n-v5.dts

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+/dts-v1/;
+
+#include "ar9331_tplink_tl-wr741nd-v4.dtsi"
+
+/ {
+	model = "TP-Link TL-WR740N v5";
+	compatible = "tplink,tl-wr740n-v5", "qca,ar9331";
+};

target/linux/ath79/image/tiny-tp-link.mk

@@ -93,6 +93,14 @@ define Device/tplink_tl-wr740n-v4
 endef
 TARGET_DEVICES += tplink_tl-wr740n-v4
 
+define Device/tplink_tl-wr740n-v5
+  $(Device/tplink-4mlzma)
+  ATH_SOC := ar9331
+  DEVICE_TITLE := TP-Link TL-WR740N v5
+  TPLINK_HWID := 0x07400005
+endef
+TARGET_DEVICES += tplink_tl-wr740n-v5
+
 define Device/tplink_tl-wr741-v1
   $(Device/tplink-4m)
   ATH_SOC := ar7240