Sysupgrade broke on x86 when grub2 superceded grub. This patch
corrects tha magic_word to be expected in grub2 combined images.
Signed-off-by: Russell Senior <russell@personaltelco.net>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@33890 3c298f89-4303-0410-b956-a3cf2f4a3e73