Rework fallback sprom support by providing different sproms for
different chips. Also make it optional to use.
This likely causes sprom fallback support to break on a few boards.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41942 3c298f89-4303-0410-b956-a3cf2f4a3e73