rtc: add driver for Maxim 77802 PMIC Real-Time-Clock

The MAX7802 PMIC has a Real-Time-Clock (RTC) with two alarms.  This
patch adds support for the RTC and is based on a driver added by Simon
Glass to the Chrome OS kernel 3.8 tree.

[akpm@linux-foundation.org: add comment clarifying ffs() use]
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Olof Johansson <olof@lixom.net>
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -298,6 +298,16 @@ config RTC_DRV_RK808
 	  This driver can also be built as a module. If so, the module
 	  will be called rk808-rtc.
 
+config RTC_DRV_MAX77802
+	tristate "Maxim 77802 RTC"
+	depends on MFD_MAX77686
+	help
+	  If you say yes here you will get support for the
+	  RTC of Maxim MAX77802 PMIC.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-max77802.
+
 config RTC_DRV_RS5C372
 	tristate "Ricoh R2025S/D, RS5C372A/B, RV5C386, RV5C387A"
 	help

drivers/rtc/Makefile

@@ -85,6 +85,7 @@ obj-$(CONFIG_RTC_DRV_MAX8998)	+= rtc-max8998.o
 obj-$(CONFIG_RTC_DRV_MAX8997)	+= rtc-max8997.o
 obj-$(CONFIG_RTC_DRV_MAX6902)	+= rtc-max6902.o
 obj-$(CONFIG_RTC_DRV_MAX77686)	+= rtc-max77686.o
+obj-$(CONFIG_RTC_DRV_MAX77802)  += rtc-max77802.o
 obj-$(CONFIG_RTC_DRV_MC13XXX)	+= rtc-mc13xxx.o
 obj-$(CONFIG_RTC_DRV_MCP795)	+= rtc-mcp795.o
 obj-$(CONFIG_RTC_DRV_MSM6242)	+= rtc-msm6242.o