device: allow to use dummy as a way to test streamer

This adds loopback tests via `tests/`

device/dummy/device.c

@@ -5,6 +5,7 @@
 
 int dummy_device_open(device_t *dev)
 {
+  dev->opts.allow_dma = false;
   dev->dummy = calloc(1, sizeof(device_dummy_t));
   return 0;
 }