ar71xx: add support for TP-Link TL-WR942N v1

TP-Link TL-WR942N v1 is a 2.4 GHz single-band N450 router, based on
Qualcomm/Atheros QCA9561.

Specification:

- 775/650/258 MHz (CPU/DDR/AHB)
- 128 MB of RAM (DDR2)
- 16 MB of FLASH (SPI NOR)
- 3T3R 2.4 GHz
- 5x 10/100 Mbps Ethernet
- 2x USB 2.0
- 11x LED (most are controlled by 74HC595)
- 2x button
- UART header on PCB*

* Serial console is disabled in OEM non-beta firmwares and corresponding
  GPIO pins 14 and 15 are assigned to control USB1 and USB2 LEDs by
  production (non-beta) U-Boot and firmware.

Currently not working:

1. USB1 and USB2 LEDs if UART RX and TX pins are assigned to their GPIOs
   by some U-Boot versions.

Flash instruction under vendor GUI:

1. Download "lede-ar71xx-generic-tl-wr942n-v1-squashfs-factory.bin".
2. Go to WEB interface and perform usual firmware upgrade.

FLash instruction under U-Boot recovery mode (doesn't work in beta
firmware):

1. Setup PC with static IP "192.168.0.66/24" and tftp server.
2. Change "*-factory" image filename to "WR942v1_recovery.bin" and make
   it available to download from your tftp server.
3. Press "reset" button and power up the router, wait till "WPS" LED
   turns on.

Flash instruction under U-Boot, using UART (can be done only with
preinstalled UART-enabled U-Boot version!):

1. Use "tpl" to stop autobooting and obtain U-Boot CLI access.
2. Setup ip addresses for U-Boot and your tftp server.
3. Issue below commands:
   tftp 0x81000000 lede-ar71xx-generic-tl-wr942n-v1-sysupgrade.bin
   erase 0x9f020000 +$filesize
   cp.b 0x81000000 0x9f020000 $filesize
   reset

Signed-off-by: Serg Studzinskii <serguzhg@gmail.com>
[minor code style fixes, extended commit message]
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

tools/firmware-utils/src/tplink-safeloader.c

@@ -553,6 +553,43 @@ static struct device_info boards[] = {
 		.last_sysupgrade_partition = "file-system"
 	},
 
+	/** Firmware layout for the TL-WR942N V1 */
+	{
+		.id     = "TLWR942NV1",
+		.vendor = "",
+		.support_list =
+			"SupportList:\r\n"
+			"{product_name:TL-WR942N,product_ver:1.0.0,special_id:00000000}\r\n"
+			"{product_name:TL-WR942N,product_ver:1.0.0,special_id:52550000}\r\n",
+		.support_trail = '\x00',
+		.soft_ver = NULL,
+
+		.partitions = {
+			{"fs-uboot", 0x00000, 0x20000},
+			{"os-image", 0x20000, 0x150000},
+			{"file-system", 0x170000, 0xcd0000},
+			{"default-mac", 0xe40000, 0x00200},
+			{"pin", 0xe40200, 0x00200},
+			{"product-info", 0xe40400, 0x0fc00},
+			{"partition-table", 0xe50000, 0x10000},
+			{"soft-version", 0xe60000, 0x10000},
+			{"support-list", 0xe70000, 0x10000},
+			{"profile", 0xe80000, 0x10000},
+			{"default-config", 0xe90000, 0x10000},
+			{"user-config", 0xea0000, 0x40000},
+			{"qos-db", 0xee0000, 0x40000},
+			{"certificate", 0xf20000, 0x10000},
+			{"usb-config", 0xfb0000, 0x10000},
+			{"log", 0xfc0000, 0x20000},
+			{"radio-bk", 0xfe0000, 0x10000},
+			{"radio", 0xff0000, 0x10000},
+			{NULL, 0, 0}
+		},
+
+		.first_sysupgrade_partition = "os-image",
+		.last_sysupgrade_partition = "file-system",
+	},
+
 	/** Firmware layout for the RE450 */
 	{
 		.id = "RE450",