mfd: Convert twl6040 to i2c driver, and separate it from twl core

Complete the separation of the twl6040 from the twl core since
it is a separate chip, not part of the twl6030 PMIC.

Make the needed Kconfig changes for the depending drivers at the
same time to avoid breaking the kernel build (vibra, ASoC components).

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonicro.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 29f463c..11e44386 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -268,10 +268,17 @@
 	  This is used to control charging LED brightness.
 
 config TWL6040_CORE
-	bool
-	depends on TWL4030_CORE && GENERIC_HARDIRQS
+	bool "Support for TWL6040 audio codec"
+	depends on I2C=y && GENERIC_HARDIRQS
 	select MFD_CORE
+	select REGMAP_I2C
 	default n
+	help
+	  Say yes here if you want support for Texas Instruments TWL6040 audio
+	  codec.
+	  This driver provides common support for accessing the device,
+	  additional drivers must be enabled in order to use the
+	  functionality of the device (audio, vibra).
 
 config MFD_STMPE
 	bool "Support STMicroelectronics STMPE"