migration: remove unfreeze logic

Now that we have a thread, and blocking writes, we don't need it.

Signed-off-by: Juan Quintela <quintela@redhat.com>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

include/migration/migration.h

@@ -82,7 +82,6 @@ void migrate_fd_connect(MigrationState *s);
 ssize_t migrate_fd_put_buffer(MigrationState *s, const void *data,
                               size_t size);
 void migrate_fd_put_ready(MigrationState *s);
-int migrate_fd_wait_for_unfreeze(MigrationState *s);
 int migrate_fd_close(MigrationState *s);
 
 void add_migration_state_change_notifier(Notifier *notify);