ath79: add support for Bluesocket BSAP1880 board

ath79: add support for Bluesocket BSAP1880 board

This board was used in dual-band 802.11n enterprise access points, models
BSAP-1800v2 and BSAP-1840, introduced in 2010 by Bluesocket, which was
acquired by Adtran in 2011, who has now EOL'ed them. They differed only in
that the BSAP-1840's antennae were detachable, while the BSAP-1800v2's were
inside the case. They have an external RJ-45 console port, which works with
standard Cisco 72-3383-01 console cables.

Specification:
- System-On-Chip: AR7161
- CPU/Speed: 600 MHz
- Flash-Chip: Macronix MX25L12845E
- Flash size: 16 MiB
- RAM: 64 MiB
- Wireless No1: Lite-On WN2601A card: AR9160/AR9103 2.4GHz 802.11bgn
- Wireless No2: Lite-On WN2502A card: AR9160/AR9106 5GHz 802.11an
- PHY: Vitesse VSC8601, Rev. B

Installation:
1. Connect to the serial console using a terminal that supports YMODEM at
   115200 bps, 8 data bits, no parity, 1 stop bit
2. Interrupt the bootloader using its password, which is: r00t
3. Issue the "fis init" command, confirming if prompted
4. Look at the length of the openwrt-ath79-generic-*-squashfs-kernel.bin
   file, and substitute it below, instead of where I have "LeNgTh"
5. Issue the following command, and upload this file using YMODEM protocol
   load -r -v -b 0x80060000 -m ymodem
6. Issue the following commands, substituting as mentioned above:
   fis create -b 0x80060000 -l LeNgTh vmlinux_2
   load -r -v -b 0x80100000 -m ymodem
7. Using YMODEM, upload openwrt-ath79-generic-*-squashfs-rootfs.bin
8. Issue the "fis free" command, and for the first range in its response,
   use a hexadecimal calculator to subtract the start from the end in order
   to substitute it below, with the leading "0x" to specify it in
   hexadecimal, instead of where I have "LeNgTh"
9. Issue the following commands, substituting as mentioned above:
   fis create -b 0x80100000 -l LeNgTh -e 0 -r 0 rootfs
   reset
10.Wait for the status LED to go solid green

Tested-by: Brian Gonyer <bgonyer@gmail.com>
Signed-off-by: Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>
[fixed obsolete $ARGV in platform_do_upgrade]
Signed-off-by: Petr Štetiar <ynezz@true.cz>