ASoC: atmel_ssc_dai: Don't unconditionally reset SSC on stream startup

commit cbaadf0f ("ASoC: atmel_ssc_dai: refactor the startup and
shutdown") refactored code such that the SSC is reset on every
startup; this breaks duplex audio (e.g. first start audio playback,
then start record, causing the playback to stop/hang)

Fixes: cbaadf0f (ASoC: atmel_ssc_dai: refactor the startup and shutdown)
Signed-off-by: Christoph Huber <c.huber@bct-electronic.com>
Signed-off-by: Peter Meerwald-Stadler <p.meerwald@bct-electronic.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

sound/soc/atmel/atmel_ssc_dai.c

@@ -299,7 +299,8 @@ static int atmel_ssc_startup(struct snd_pcm_substream *substream,
 	clk_enable(ssc_p->ssc->clk);
 	ssc_p->mck_rate = clk_get_rate(ssc_p->ssc->clk);
 
-	/* Reset the SSC to keep it at a clean status */
+	/* Reset the SSC unless initialized to keep it in a clean state */
+	if (!ssc_p->initialized)
 		ssc_writel(ssc_p->ssc->regs, CR, SSC_BIT(CR_SWRST));
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {