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/Makefile b/drivers/mfd/Makefile
index 79dd22d..2a4108d 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -92,6 +92,7 @@
 
 obj-$(CONFIG_MFD_MAX77686)	+= max77686.o max77686-irq.o
 obj-$(CONFIG_MFD_MAX77693)	+= max77693.o max77693-irq.o
+obj-$(CONFIG_MFD_MAX8907)	+= max8907.o
 max8925-objs			:= max8925-core.o max8925-i2c.o
 obj-$(CONFIG_MFD_MAX8925)	+= max8925.o
 obj-$(CONFIG_MFD_MAX8997)	+= max8997.o max8997-irq.o