rtc: AB3100 RTC support

This adds support for the RTC found inside the AB3100 Mixed Signal chip.
The symbols used for communicating with the chip is found in the
mfd/ab3100-core.c driver that also provides the platform device.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Acked-by: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index b136299..73771b0 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -545,6 +545,15 @@
 	  If you say yes here you get support for the RTC subsystem of the
 	  NXP PCF50633 used in embedded systems.
 
+config RTC_DRV_AB3100
+	tristate "ST-Ericsson AB3100 RTC"
+	depends on AB3100_CORE
+	default y if AB3100_CORE
+	help
+	  Select this to enable the ST-Ericsson AB3100 Mixed Signal IC RTC
+	  support. This chip contains a battery- and capacitor-backed RTC.
+
+
 comment "on-CPU RTC drivers"
 
 config RTC_DRV_OMAP