ath79: add support for LibreRouter v1

ath79: add support for LibreRouter v1

Hardware
--------
SOC:   QCA9558
RAM:   128M DDR2
Flash: 16MiB SPI-NOR
ETH:   QCA8337N: 2x 10/100/1000 PoE and PoE pass-through
WiFi2: QCA9558 (bgn) 2T2R
WiFi5: 2x mPCIE with AR9582 (an) 2T2R
BTN:   1x Reset
GPIO:  multiple GPIO on header, PoE passthrough enable
UART:  3.3V 115200 8N1 header on the board
WDG:   ATTiny13 watchdog
JTAG:  header on the board
USB:   1x connector and 1x header on the board
PoE:   10-32V input in ETH port 1, passthrough in port 2
mPCIE: 2x populated with radios (but replaceable)

OpenWrt is preinstalled from factory. To install use <your-image>-sysupgade.bin
using the web interface or with sysupgrade -n.

Flash from bootloader (in case failsafe does not work)
1. Connect the LibreRouter with a serial adapter (TTL voltage) to the UART
   header in the board.
2. Connect an ETH cable and configure static ip addres 192.168.1.10/24
3. Turn on the device and stop the bootloader sending any key through the serial
   interface.
4. Use a TFTP server to serve <your image>-sysupgrade.bin file.
5. Execute the following commands at the bootloader prompt:
    ath> tftp 82000000 <your image>-sysupgrade.bin
    ath> erase 0x9f050000 +$filesize
    ath> cp.b 0x82000000 0x9f050000 $filesize
    ath> bootm 0x9f050000

More docs
* Bootloader https://github.com/librerouterorg/u-boot
* Board details (schematics, gerbers): https://github.com/librerouterorg/board

Signed-off-by: Santiago Piccinini <spiccinini@altermundi.net>