AA: ar71xx: add support for the Ubiquiti UniFi AP-Outdoor device

AA: ar71xx: add support for the Ubiquiti UniFi AP-Outdoor device

Backport of r34196.

[juhosg:
  - rename and refresh 660-MIPS-ath79-ubnt-xm-add-unifi-outdoor patches
  - wrap long lines in mach-ubnt-xm
  - remove default network config, set it from uci-defaults/network
    instead
  - remove user-space, and image generation stuff]

Signed-off-by: Daniel Dickinson <daniel@powercloudsystems.com>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@34341 3c298f89-4303-0410-b956-a3cf2f4a3e73