travis.yml: Test the s390-ccw build, too

travis.yml: Test the s390-ccw build, too

Since we can now use a s390x host on Travis, we can also build and
test the s390-ccw bios images there. For this we have to make sure
that roms/SLOF is checked out, too, and then move the generated *.img
files to the right location before running the tests.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200206202543.7085-1-thuth@redhat.com>
Message-Id: <20200225124710.14152-6-alex.bennee@linaro.org>