ar71xx: add support for WHQX E1700AC/E600G/E600GAC v2

ar71xx: add support for WHQX E1700AC/E600G/E600GAC v2

WHQX E1700AC v2 is based on Qualcomm QCA9563 + QCA9880 + QCA8334.

Specification:

- 750/400/250 MHz (CPU/DDR/AHB)
- 128 MB of RAM (DDR2)
- 8/16 MB of FLASH (SPI NOR)
- 3T3R 2.4 GHz (QCA9563) with external FEM (SKY85309-11)
- 3T3R 5 GHz (QCA9880) with external FEM (SKY85728-11)
- 2x 10/100/1000 Mbps Ethernet (one port with PoE support)
- 1x miniPCIe slot (USB 2.0 bus only)
- 1x microSIM slot
- 1x USB 2.0
- 5x LED (4 driven by GPIO)
- 1x button (reset)
- 1x 2-pos switch
- 1x DC jack for main power input (9-48 V)
- UART (J5) and LEDs (J13) headers on PCB

WHQX E600G is based on Qualcomm QCA9531.

Specification:

- 650/391/216 MHz (CPU/DDR/AHB)
- 64/128 MB of RAM (DDR2)
- 8/16 MB of FLASH (SPI NOR)
- 2T2R 2.4 GHz (QCA9531) with external PA (LXK-6601)
- 2x 10/100 Mbps Ethernet (one port with PoE support)
- 1x miniPCIe slot (with PCIe and USB 2.0 buses)
- 1x microSIM slot
- 5x LED (4 driven by GPIO)
- 1x button (reset)
- 1x DC jack for main power input (9-48 V)
- UART (J100), SIM (J34), JTAG (J5) and LEDs (J7) headers on PCB

WHQX E600GAC is based on Qualcomm QCA9531 + QCA9887.

Specification:

- 650/391/216 MHz (CPU/DDR/AHB)
- 64/128 MB of RAM (DDR2)
- 8/16 MB of FLASH (SPI NOR)
- 2T2R 2.4 GHz (QCA9531)
- 1T1R 5 GHz (QCA9887) with external FEM (SKY85703-11)
- 2x 10/100 Mbps Ethernet
- 6x LED (1x RGB, 5 driven by GPIO)
- 1x button (reset)
- 1x DC jack for main power input (9-12 V)
- UART (J100), USB (J102), JTAG (J5) and LEDs (J7) header on PCB

Important notice:

First version of these boards are using different mtd layout, with ART
data at the end. You should not use v2 images on v1 board because it
will result in lost of ART data!

Flash instruction (using U-Boot CLI and tftp server):

1. Configure PC with static IP 192.168.1.10 and tftp server.
2. Rename "sysupgrade" filename to "firmware.bin" and place it in tftp
   server directory.
3. Connect PC with one of RJ45 ports, power up the board and press
   "enter" key to access U-Boot CLI.
4. Use the following command to update the device to OpenWrt: "run lfw".

Flash instruction (using U-Boot web-based recovery):

1. Configure PC with static IP 192.168.1.xxx(2-254)/24.
2. Connect PC with one of RJ45 ports, press the reset button, power up
   the board and keep button pressed for around 6-7 seconds, until LEDs
   start flashing.
3. Open your browser and enter 192.168.1.1, select "sysupgrade" image
   and click the upgrade button.

Signed-off-by: Peng Zhang <sd20@qxwlan.com>
[reworked: image generation code, mach-* files, commit description,
fixed minor code style issues, rebased on master]
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>