ar71xx: Add support for PISEN TS-D084

PISEN TS-D084 is an wireless router with a battery and integrated power supply based on Atheros AR9331.

Specification:

- 400/400/200 MHz (CPU/DDR/AHB)
- 64 MB of RAM (DDR2)
- 8 MB of FLASH (SPI NOR)
- 1x 10/100 Mbps Ethernet
- 1T1R 2.4 GHz (AR9331)
- 1x USB 2.0

Flash instruction:
The manufacturer are using exactly the same firmware header as TP-LINK TL-WR703N (including device ID!). Simply upload the factory firmware into WebUI and flashing is done.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

target/linux/ar71xx/base-files/lib/ar71xx.sh

@@ -1325,6 +1325,9 @@ ar71xx_board_detect() {
 	*"TL-WR942N v1")
 		name="tl-wr942n-v1"
 		;;
+	*"TS-D084")
+		name="ts-d084"
+		;;
 	*"Tube2H")
 		name="tube2h"
 		;;