regulator: add MAX8907 driver

The MAX8907 is an I2C-based power-management IC containing voltage
regulators, a reset controller, a real-time clock, and a touch-screen
controller.

The original driver was written by:
* Gyungoh Yoo <jack.yoo@maxim-ic.com>

Various fixes and enhancements by:
* Jin Park <jinyoungp@nvidia.com>
* Tom Cherry <tcherry@nvidia.com>
* Prashant Gaikwad <pgaikwad@nvidia.com>
* Dan Willemsen <dwillemsen@nvidia.com>
* Laxman Dewangan <ldewangan@nvidia.com>

During upstreaming, I (swarren):
* Converted to regmap.
* Allowed probing from device tree.
* Reworked the regulator driver to be represented as a single device that
  provides multiple regulators, rather than as a device per regulator.
* Replaced many regulator ops with standard functions.
* Added ability to specify supplies for each regulator.
* Removed the WLED regulator. If/when we expose this in the driver, it
  should be a backlight object not a regulator object.
* Renamed from max8907c->max8907, since the driver covers at least the
  C and B revisions.
* General cleanup.

Signed-off-by: Gyungoh Yoo <jack.yoo@maxim-ic.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/Kconfig

@@ -172,6 +172,14 @@ config REGULATOR_MAX8660
 	  This driver controls a Maxim 8660/8661 voltage output
 	  regulator via I2C bus.
 
+config REGULATOR_MAX8907
+	tristate "Maxim 8907 voltage regulator"
+	depends on MFD_MAX8907
+	help
+	  This driver controls a Maxim 8907 voltage output regulator
+	  via I2C bus. The provided regulator is suitable for Tegra
+	  chip to control Step-Down DC-DC and LDOs.
+
 config REGULATOR_MAX8925
 	tristate "Maxim MAX8925 Power Management IC"
 	depends on MFD_MAX8925

drivers/regulator/Makefile

@@ -30,6 +30,7 @@ obj-$(CONFIG_REGULATOR_LP8788) += lp8788-ldo.o
 obj-$(CONFIG_REGULATOR_MAX1586) += max1586.o
 obj-$(CONFIG_REGULATOR_MAX8649)	+= max8649.o
 obj-$(CONFIG_REGULATOR_MAX8660) += max8660.o
+obj-$(CONFIG_REGULATOR_MAX8907) += max8907-regulator.o
 obj-$(CONFIG_REGULATOR_MAX8925) += max8925-regulator.o
 obj-$(CONFIG_REGULATOR_MAX8952) += max8952.o
 obj-$(CONFIG_REGULATOR_MAX8997) += max8997.o