mkelfimage is about to be removed, so test_devtool_modify_git needs to
use a different recipe. psplash is a reasonable choice given it uses a
git repository (and probably will forever), and doesn't have too many
dependencies, so change the test to use that recipe instead.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
