migration: Don't return for postcopy_send_discard_bm_ram()

postcopy_send_discard_bm_ram() always return zero. Since it can't
fail, simplify and do not return anything.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
1 file changed