ath79: add support for Belkin F9J1108v2 (AC1750 DB Wi-Fi)

ath79: add support for Belkin F9J1108v2 (AC1750 DB Wi-Fi)

This device is the non-US build of the F9K1115 v2, with a different
firmware magic.

Specifications:

SoC: QCA9558
CPU: 720 MHz
Flash: 16 MiB NOR
RAM: 128 MiB
WiFi 2.4 GHz: QCA9558-AT4A 3x3 MIMO 802.11b/g/n
WiFi 5 GHz: QCA9880-2R4E 3x3 MIMO 802.11a/n/ac
Ethernet: 4x LAN and 1x WAN (all 1gbps)
USB: 1 x USB 2.0 (lower), 1 x USB 3.0 (upper)

MAC addresses based on OEM firmware:

Interface   Address   Location
---------   -------   --------
lan         *:5A      sometimes in 0x6
wan         *:5B      0x0
2.4Ghz      *:5A      0x1002
5Ghz        As per mini PCIe EEPROM

Flashing instructions:

The factory.bin can be flashed via the Belkin web UI or via the uboot
http upgrade page.
Once the factory.bin has been written, sysupgrade.bin will work as usual.

Signed-off-by: Damien Mascord <tusker@tusker.org>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
[wrap commit message/code, adjust label-mac-device, whitespace fixes,
merge block in 02_network]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>