ASoC: Add dummy S/PDIF codec support

McASP on DM646x can operate in DIT (S/PDIF) where no codec is needed.
This patch provides stub codec that can be used in these configurations.
On DM646x EVM the McASP1 is connected to the S/PDIF out.

Signed-off-by: Steve Chen <schen@mvista.com>
Signed-off-by: Pavel Kiryukhin <pkiryukhin@ru.mvista.com>
Signed-off-by: Naresh Medisetty <naresh@ti.com>
Signed-off-by: Chaithrika U S <chaithrika@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index cb07d9b..bbc97fd 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -18,6 +18,7 @@
 	select SND_SOC_AK4535 if I2C
 	select SND_SOC_CS4270 if I2C
 	select SND_SOC_PCM3008
+	select SND_SOC_SPDIF
 	select SND_SOC_SSM2602 if I2C
 	select SND_SOC_STAC9766 if SND_SOC_AC97_BUS
 	select SND_SOC_TLV320AIC23 if I2C
@@ -91,6 +92,9 @@
 config SND_SOC_PCM3008
        tristate
 
+config SND_SOC_SPDIF
+	tristate
+
 config SND_SOC_SSM2602
 	tristate