regulator: Add WM831x DC-DC buck convertor support

The WM831x series of devices all have 3 DC-DC buck convertors. This
driver implements software control for these regulators via the
regulator API.  Use with split hardware/software control of individual
regulators is not supported, though regulators not controlled by
software may be controlled via the hardware control interfaces.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index da7483e..38ea5dc 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -82,6 +82,13 @@
 	  This driver supports the voltage regulators provided by
 	  this family of companion chips.
 
+config REGULATOR_WM831X
+	tristate "Wolfson Microelcronics WM831x PMIC regulators"
+	depends on MFD_WM831X
+	help
+	  Support the voltage and current regulators of the WM831x series
+	  of PMIC devices.
+
 config REGULATOR_WM8350
 	tristate "Wolfson Microelectroncis WM8350 AudioPlus PMIC"
 	depends on MFD_WM8350