hwmon: Add MCP3021 ADC driver

Add I2C driver for MCP3021 that is an ADC chip from Microchip.
The MCP3021 is a successive approximation A/D converter (ADC)
with 10-bit resolution.
The driver export the value of Vin to sysfs, the voltage unit is
mV. Through the sysfs interface, lm-sensors tool can also display
Vin voltage.

Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Xie Xiaobo <X.Xie@freescale.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 7190a3f..5b32d56 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -813,6 +813,16 @@
 	  This driver can also be built as a module.  If so, the module
 	  will be called max6650.
 
+config SENSORS_MCP3021
+	tristate "Microchip MCP3021"
+	depends on I2C && EXPERIMENTAL
+	help
+	  If you say yes here you get support for the MCP3021 chip
+	  that is a A/D converter (ADC) with 10-bit resolution.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called mcp3021.
+
 config SENSORS_NTC_THERMISTOR
 	tristate "NTC thermistor support"
 	depends on EXPERIMENTAL