[media] tm6000: Plug memory leak on PCM free

When releasing hardware resources, the DMA buffer allocated to the PCM
device needs to be freed to prevent a memory leak.
Signed-off-by: NThierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/tm6000/tm6000-alsa.c

@@ -304,6 +304,7 @@ static int snd_tm6000_hw_free(struct snd_pcm_substream *substream)
 		schedule_work(&core->wq_trigger);
 	}
 
+	dsp_buffer_free(substream);
 	return 0;
 }