libvduse: Fix the incorrect function name

In vduse_name_is_valid(), we actually check whether
the name is invalid or not. So let's change the
function name to vduse_name_is_invalid() to match
the behavior.

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20220706095624.328-2-xieyongji@bytedance.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>