ASoC: max9768: add driver for max9768 amplifier

Add a driver supporting the volume control and the mute pin. Shdn pin
and DAPM are not taken care of yet.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index 39aec3c..6508e8b 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -40,6 +40,7 @@
 	select SND_SOC_MAX98088 if I2C
 	select SND_SOC_MAX98095 if I2C
 	select SND_SOC_MAX9850 if I2C
+	select SND_SOC_MAX9768 if I2C
 	select SND_SOC_MAX9877 if I2C
 	select SND_SOC_PCM3008
 	select SND_SOC_RT5631 if I2C
@@ -429,6 +430,9 @@
 config SND_SOC_LM4857
 	tristate
 
+config SND_SOC_MAX9768
+	tristate
+
 config SND_SOC_MAX9877
 	tristate