atapi: fix halted DMA reset

Followup to 87ac25fd, this time for ATAPI DMA.

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1470164128-28158-1-git-send-email-jsnow@redhat.com
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>

hw/ide/atapi.c

@@ -386,6 +386,7 @@ static void ide_atapi_cmd_read_dma_cb(void *opaque, int ret)
     if (ret < 0) {
         if (ide_handle_rw_error(s, -ret, ide_dma_cmd_to_retry(s->dma_cmd))) {
             if (s->bus->error_status) {
+                s->bus->dma->aiocb = NULL;
                 return;
             }
             goto eot;