ASoC: Move AC'97 support to its own file

Currently the AC'97 support is splattered all throughout soc-core.c. Some
parts are #ifdef'd some parts are not. This patch moves the AC'97 support to
its own file, this should make the code a bit more clearer and also makes it
possible to easily not compile it into the kernel when not needed.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/Makefile b/sound/soc/Makefile
index 534714a..0fded1b 100644
--- a/sound/soc/Makefile
+++ b/sound/soc/Makefile
@@ -5,6 +5,10 @@
 snd-soc-core-objs += soc-generic-dmaengine-pcm.o
 endif
 
+ifneq ($(CONFIG_SND_SOC_AC97_BUS),)
+snd-soc-core-objs += soc-ac97.o
+endif
+
 obj-$(CONFIG_SND_SOC)	+= snd-soc-core.o
 obj-$(CONFIG_SND_SOC)	+= codecs/
 obj-$(CONFIG_SND_SOC)	+= generic/