[lantiq] add VG3503J support

[lantiq] add VG3503J support

this adds basic support. the bootloader on these units is locked down.

until we have a replacement we can do basic testing with these env variables in uboot.

set update_openwrt erase 0xb0020000 0xb073ffff \;tftp 0x81000000 openwrt-lantiq-xway-VG3503J-squashfs.image\;cp.b 0x81000000 0xb0020000 \$(filesize)
set bootcmd cp.b 0xb0020000 0x80002000 0x400000\; go 0x80002000

unfortunatley the bootloader ignores the bootcmd, so autobooting is not possible yet. you need to call "run bootcmd" by hand after each power cycle.

please note that the vdsl firmware is non redistributable. you can find it in the GPL drop that BT provides.

Signed-off-by: John Crispin <blogic@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36315 3c298f89-4303-0410-b956-a3cf2f4a3e73