drivers: regulator: add Maxim 8998 driver

Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

This patch adds voltage regulator driver for Maxim 8998 chip. This chip
is used on Samsung Aquila and GONI boards and provides following
functionalities:
- 4 BUCK voltage converters, 17 LDO power regulators and 5 other power
  controllers
- battery charger

This patch adds basic driver for voltage regulators and MAX 8998 MFD core.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 9da0e50..ad61a9e 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -252,6 +252,16 @@
 	  accessing the device, additional drivers must be enabled in order
 	  to use the functionality of the device.
 
+config MFD_MAX8998
+	bool "Maxim Semiconductor MAX8998 PMIC Support"
+	depends on I2C=y
+	select MFD_CORE
+	help
+	  Say yes here to support for Maxim Semiconductor MAX8998. This is
+	  a Power Management IC. This driver provies common support for
+	  accessing the device, additional drivers must be enabled in order
+	  to use the functionality of the device.
+
 config MFD_WM8400
 	tristate "Support Wolfson Microelectronics WM8400"
 	select MFD_CORE