hw/misc/edu: add msi_uninit() for pci_edu_uninit()

hw/misc/edu: add msi_uninit() for pci_edu_uninit()

Let's supplement the msi_uninit() when failing to realize
the pci edu device.

Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Fei Li <shirley17fei@gmail.com>
Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>