ASoC: dmaengine_pcm: Reset pointer position when starting a stream

Otherwise a wrong position will be reported after restarting a stream and the
first few samples might be skipped.
Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-dmaengine-pcm.c

@@ -142,6 +142,7 @@ static int dmaengine_pcm_prepare_and_submit(struct snd_pcm_substream *substream)
 
 	direction = snd_pcm_substream_to_dma_direction(substream);
 
+	prtd->pos = 0;
 	desc = chan->device->device_prep_dma_cyclic(chan,
 		substream->runtime->dma_addr,
 		snd_pcm_lib_buffer_bytes(substream),