scsi-disk: add missing break

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi/scsi-disk.c

@@ -2740,6 +2740,7 @@ static int32_t scsi_block_dma_command(SCSIRequest *req, uint8_t *buf)
         /* 10-byte CDB.  */
         r->cdb1 = req->cmd.buf[1];
         r->group_number = req->cmd.buf[6];
+        break;
     case 4:
         /* 12-byte CDB.  */
         r->cdb1 = req->cmd.buf[1];