ramips: fix sysupgrade for asiarf awm003

Since the earlier r41797 change, the board_name for awm003 has been
miscalculated, and sysupgrade has been broken.  This seems to fix it.

Signed-off-by: Russell Senior <russell@personaltelco.net>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41837 3c298f89-4303-0410-b956-a3cf2f4a3e73