Changing APPEND wasn't causing syslinux to re-run, so add a manual dependency.
(From OE-Core rev: 3c2d7ae5d59cb76a838f227c4cb0c64cea0d9e03)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>