power: pm8xxx-ccadc: Add pm8xxx ccadc subdevice

Until now only the BMS system was using the ccadc so there was
no need to create a separate ccadc driver.

However we can run in a configuration with BMS disabled
and clients won't be able to read battery current via ccadc.

Separate the ccadc from the bms, this change in is preparation
to add a ccadc api to read the battery current.

Change-Id: Ib96b146d91d01d196df9291eb23432cd430db4d0
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index 3590e6d..7c8dfea 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -332,7 +332,14 @@
 	help
 	  Say Y here to enable support for pm8921 chip charger subdevice
 
+config PM8XXX_CCADC
+	tristate "PM8XXX battery current adc driver"
+	depends on MFD_PM8921_CORE
+	help
+	  Say Y here to enable support for pm8921 chip bms subdevice
+
 config PM8921_BMS
+	select PM8XXX_CCADC
 	tristate "PM8921 Battery Monitoring System driver"
 	depends on MFD_PM8921_CORE
 	help