ASoC: soc-pcm: add missing ret=0 at soc_pcm_open()

commit 140a453 ("ASoC: soc-pcm: add soc_pcm_clean() and call it
from soc_pcm_open/close()") switched to use soc_pcm_clean() at
soc_pcm_open().

But it removed "return 0", and missing "ret = 0",
because of it, it always return -EINVAL eventhough no error.
This patch adds missing "ret = 0" for success case.

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/87ft6ya65z.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-pcm.c

@@ -784,6 +784,7 @@ static int soc_pcm_open(struct snd_pcm_substream *substream)
 		 runtime->hw.rate_max);
 dynamic:
 	snd_soc_runtime_activate(rtd, substream->stream);
+	ret = 0;
 err:
 	mutex_unlock(&rtd->card->pcm_mutex);
 pm_err: