ASoC: Add PCM1681 codec driver.

PCM1681 can be controlled via I2C, SPI or in bootstrap mode (no control mode). This code add
support only for I2C mode.

Signed-off-by: Marek Belisko <marek.belisko@streamunlimited.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index badb6fb..e2daf82 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -54,6 +54,7 @@
 	select SND_SOC_MC13783 if MFD_MC13XXX
 	select SND_SOC_ML26124 if I2C
 	select SND_SOC_HDMI_CODEC
+	select SND_SOC_PCM1681 if I2C
 	select SND_SOC_PCM3008
 	select SND_SOC_RT5631 if I2C
 	select SND_SOC_RT5640 if I2C
@@ -292,6 +293,9 @@
 config SND_SOC_HDMI_CODEC
        tristate
 
+config SND_SOC_PCM1681
+       tristate
+
 config SND_SOC_PCM3008
        tristate