mfd: ac100: Add driver for X-Powers AC100 audio codec / RTC combo IC

The AC100 is a multifunction device with an audio codec subsystem and
an RTC subsystem. These two subsystems share a common register space
and host interface.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 2ba3ba3..bca83db 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -113,6 +113,8 @@
 obj-$(CONFIG_PMIC_DA9052)	+= da9052-core.o
 obj-$(CONFIG_MFD_DA9052_SPI)	+= da9052-spi.o
 obj-$(CONFIG_MFD_DA9052_I2C)	+= da9052-i2c.o
+
+obj-$(CONFIG_MFD_AC100)		+= ac100.o
 obj-$(CONFIG_MFD_AXP20X)	+= axp20x.o
 obj-$(CONFIG_MFD_AXP20X_I2C)	+= axp20x-i2c.o
 obj-$(CONFIG_MFD_AXP20X_RSB)	+= axp20x-rsb.o