ASoC: Add simplfied device registration for Atmel SSC devices

Since the SSC is already being registered as a device under arch and
the DMA and SSC hardware are pretty much the same provide a simplified
device registration function for the Atmel SSC which will add the
ASoC-specific devices within the ASoC code, parenting the SSC device
off the actual SSC device. Also use it in the sam9g20-ek driver.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

sound/soc/atmel/sam9g20_wm8731.c

@@ -205,6 +205,12 @@ static int __init at91sam9g20ek_init(void)
 	if (!(machine_is_at91sam9g20ek() || machine_is_at91sam9g20ek_2mmc()))
 		return -ENODEV;
 
+	ret = atmel_ssc_set_audio(0);
+	if (ret != 0) {
+		pr_err("Failed to set SSC 0 for audio: %d\n", ret);
+		return ret;
+	}
+
 	/*
 	 * Codec MCLK is supplied by PCK0 - set it up.
 	 */