mfd: Add ChromeOS EC I2C driver

This uses an I2C bus to talk to the ChromeOS EC. The protocol
is defined by the EC and is fairly simple, with a length byte,
checksum, command byte and version byte (to permit easy creation
of new commands).

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 967767d..895257b 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -9,6 +9,7 @@
 obj-$(CONFIG_MFD_SM501)		+= sm501.o
 obj-$(CONFIG_MFD_ASIC3)		+= asic3.o tmio_core.o
 obj-$(CONFIG_MFD_CROS_EC)	+= cros_ec.o
+obj-$(CONFIG_MFD_CROS_EC_I2C)	+= cros_ec_i2c.o
 
 rtsx_pci-objs			:= rtsx_pcr.o rts5209.o rts5229.o rtl8411.o rts5227.o
 obj-$(CONFIG_MFD_RTSX_PCI)	+= rtsx_pci.o