ar71xx: PowerCloud CAP324 image generation

Image generation (and mtd partition) part of support for
PowerCloud CAP324 Cloud AP. The CAP324 Cloud AP is a device sold by
PowerCloud Systems who's stock firmware (CloudCommand) provides
'cloud' based managment of large numbers of access points.

The CAP324 is a dual-band 802.11n wireless access point with 16MB flash
and 128MB RAM and single gigabit ethernet port.  It can be powered via
PoE or a power adaptor.

Signed-off-by: Daniel Dickinson <openwrt@daniel.thecshore.com>

SVN-Revision: 47941