vmstate registration: check return values

Check qdev's call to vmstate_register_with_alias_id; that gets
most of the common uses; there's hundreds of calls via vmstate_register
which could get fixed over time.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20170202125956.21942-4-dgilbert@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
