wm831x: Factor out WM831x backup battery charger

The backup battery on WM831x is a separate IP block to the main PMU
and is largely unrelated to the main supply functionality. Factor it
out into a separate driver in order to reflect this and better support
future hardware versions.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index cea6cef..783e9b7 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -29,6 +29,13 @@
 	  Say Y here to enable support APM status emulation using
 	  battery class devices.
 
+config WM831X_BACKUP
+	tristate "WM831X backup battery charger support"
+	depends on MFD_WM831X
+	help
+	  Say Y here to enable support for the backup battery charger
+	  in the Wolfson Microelectronics WM831x PMICs.
+
 config WM831X_POWER
 	tristate "WM831X PMU support"
 	depends on MFD_WM831X