ixp4xx: update Gateworks Avila board support

ixp4xx: update Gateworks Avila board support

Several new features for newer boards:
 - add additional UARTs present on some boards
 - add additional LEDs present on some boards
 - add HSS audio device codec present on some boards
 - add support for GSC present on some boards
 - add per model setup support for newer boards
 - set FLASH window per-model for boards with larger FLASH

Some fixes:
 - add IRQ mapping for additional PCI devices (USB Host)

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@33647 3c298f89-4303-0410-b956-a3cf2f4a3e73