ipq40xx: add support for Extreme Networks WS-AP3915i

ipq40xx: add support for Extreme Networks WS-AP3915i

Hardware
--------
Qualcomm IPQ4029 WiSoC
2T2R 802.11 abgn
2T2R 802.11 nac
Macronix MX25L25635E SPI-NOR (32M)
512M DDR3 RAM
1x Gigabit LAN
1x Cisco RJ-45 Console port
Settings: 115200 8N1

Installation
------------

1. Attach to the Console port. Power up the device and press the s key
   to interrupt autoboot.

2. The default username / password to the bootloader is admin / new2day

3. Update the bootcommand to allow loading OpenWrt.

   $ setenv ramboot_openwrt "setenv serverip 192.168.1.66;
     setenv ipaddr 192.168.1.1; tftpboot 0x86000000 openwrt-3915.bin;
     bootm"
   $ setenv boot_openwrt "sf probe;
     sf read 0x88000000 0x280000 0xc00000; bootm 0x88000000"
   $ setenv bootcmd "run boot_openwrt"
   $ saveenv

4. Download the OpenWrt initramfs image. Serve it using a TFTP server as
   "openwrt-3915.bin" at 192.1681.66.

5. Download & boot the OpenWrt initramfs image on the access point.

   $ run ramboot_openwrt

6. Wait for OpenWrt to start.

7. Download and transfer the sysupgrade image to the device using e.g.
   SCP.

8. Install OpenWrt to the device using "sysupgrade"

   $ sysupgrade -n /path/to/openwrt.bin

Signed-off-by: David Bauer <mail@david-bauer.net>