lantiq: add (incomplete) support for Aztech GR7000

*) can not connect to switch chip
*) only one usb port is working
*) wifi is not working

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37712 3c298f89-4303-0410-b956-a3cf2f4a3e73