mfd: Refactor wm831x AUXADC handling into a separate file

In preparation for some additional work on the wm831x AUXADC code move the
support into a separate file. This is a simple code motion patch, there
should be no functional changes.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 22a280f..0889f53 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -23,6 +23,7 @@
 
 obj-$(CONFIG_MFD_WM8400)	+= wm8400-core.o
 wm831x-objs			:= wm831x-core.o wm831x-irq.o wm831x-otp.o
+wm831x-objs			+= wm831x-auxadc.o
 obj-$(CONFIG_MFD_WM831X)	+= wm831x.o
 obj-$(CONFIG_MFD_WM831X_I2C)	+= wm831x-i2c.o
 obj-$(CONFIG_MFD_WM831X_SPI)	+= wm831x-spi.o