hwmon: pm8921-adc: Add sysfs interface

-Add sysfs interface to read PM8921 HK/XOADC
and thermistor temperature measurements mapped
through MPP's.
-Move PM8921 ADC from directory /drivers/mfd to
/drivers/hwmon for userspace clients to read ADC
through hwmon.

CRs-Fixed: 302365
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>

Conflicts:

	drivers/mfd/Kconfig
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index ef3cb2e..f9d671e 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -788,6 +788,15 @@
 	  internally uses an array of LTC2499 and EPM ADCs in a differential
 	  configuration to provide a flat set of channels that can be addressed.
 
+config SENSORS_PM8921_ADC
+	tristate "Support for Qualcomm PM8921 ADC"
+	depends on MFD_PM8921_CORE
+	help
+	  This is the ADC arbiter driver for Qualcomm PM8921 Chip.
+
+	  The driver supports reading the HKADC, XOADC and support to set and receive
+	  temperature threshold notifications using the Battery temperature module.
+
 config SENSORS_PC87360
 	tristate "National Semiconductor PC87360 family"
 	select HWMON_VID