The ixp4xx HSS firmware is needed in order to use the HSS (synchronous serial
port).  An example of where this is used is the Gateworks Avila boards to
interface to an audio codec.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@33680 3c298f89-4303-0410-b956-a3cf2f4a3e73