[ALSA] ASoC codecs: build files

This patch adds an ASoC Makefile and Kconfig for the WM8731, WM8750 and
WM9712 codecs.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Liam Girdwood <liam.girdwood@wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/soc/Kconfig b/sound/soc/Kconfig
index 200709f..288bad3 100644
--- a/sound/soc/Kconfig
+++ b/sound/soc/Kconfig
@@ -5,6 +5,9 @@
 menu "SoC audio support"
 	depends on SND!=n
 
+config SND_SOC_AC97_BUS
+	bool
+
 config SND_SOC
 	tristate "SoC audio support"
 	---help---
@@ -16,4 +19,7 @@
 	  This SoC audio support can also be built as a module.  If so, the module
 	  will be called snd-soc-core.
 
+# Supported codecs
+source "sound/soc/codecs/Kconfig"
+
 endmenu