ar71xx: add support for jjPlus JWAP230

ar71xx: add support for jjPlus JWAP230

jjPlus JWAP230 is based on Qualcomm Atheros QCA9558 + QCA8337.
Short specification:

- 720/600/200 MHz (CPU/DDR/AHB)
- 2x 10/100/1000 Mbps Ethernet
- 128 MB of RAM (DDR2)
- 16 MB of FLASH
- 3T3R 2.4 GHz with external PA (SST12LP15A), up to 28 dBm
- 3x MMCX connectors
- power input: 802.3at PoE or wide range DC (36-57 V)
- optional 802.3af PSE
- 1x mini-PCIe connector with PCIe, USB buses and SIM slot
- 1x mini-PCIe connector with PCIe bus
- 1x USB type-A connector
- 6x LED, 1x button (hardware reset)
- RS232 (MAX3223) and (E)JTAG headers

Default configuration:

- WAN on eth1 (RJ45 near LEDs with PoE input)
- LAN on eth0 (RJ45 near DC jack)
- left top LED set to be status LED
- all LEDs configurable form user space

Flash instruction (do it under U-Boot, using RS232):

1. tftp 0x80060000 lede-ar71xx-generic-jwap230-squashfs-sysupgrade.bin
2. erase 0x9f050000 +$filesize
3. cp.b $fileaddr 0x9f050000 $filesize
4. setenv bootcmd "bootm 0x9f050000"
5. saveenv && reset

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>