This code seems to be used by vmport hack, passing these values allows
to implement horizontal scroll support even when using vmport.
In case it's not supported horizontal scroll will act as a vertical one.

Signed-off-by: Dmitry Petrov <dpetroff@gmail.com>
Message-Id: <20220108153947.171861-6-dpetroff@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>