virtio-9p: Fix virtio-9p no longer building after hw-dirs branch merge

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Message-id: 1365495755-10902-1-git-send-email-hdegoede@redhat.com
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 93b48c201eb6c0404d15550a0eaa3c0f7937e35e)