mfd: Add MAX8907 core 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.
* Converted to regmap-irq.
* Allowed probing from device tree.
* 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>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com> #v3
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index d1facef..856ec00 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -476,6 +476,18 @@
 	  additional drivers must be enabled in order to use the functionality
 	  of the device.
 
+config MFD_MAX8907
+	tristate "Maxim Semiconductor MAX8907 PMIC Support"
+	select MFD_CORE
+	depends on I2C=y && GENERIC_HARDIRQS
+	select REGMAP_I2C
+	select REGMAP_IRQ
+	help
+	  Say yes here to support for Maxim Semiconductor MAX8907. This is
+	  a Power Management IC. This driver provides common support for
+	  accessing the device; additional drivers must be enabled in order
+	  to use the functionality of the device.
+
 config MFD_MAX8925
 	bool "Maxim Semiconductor MAX8925 PMIC Support"
 	depends on I2C=y && GENERIC_HARDIRQS