lantiq: vgv7519: fix board_config on dts, read mac address and set

Signed-off-by: Eddi De Pieri <eddi@depieri.net>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43109 3c298f89-4303-0410-b956-a3cf2f4a3e73