rtc: sun6i: Add sun6i RTC driver

This patch introduces the driver for the RTC in the Allwinner A31 and
A23 SoCs.

Unlike the RTC found in A10/A20 SoCs, which was part of the timer, the
RTC in A31/A23 are a separate hardware block, which also contain a few
controls for the RTC block hardware (a regulator and RTC block GPIO pin
latches), while also having separate interrupts for the alarms.

The hardware is different enough to make a different driver for it.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Varka Bhadram <varkabhadram@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 56f061c..9055b7d 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -128,6 +128,7 @@
 obj-$(CONFIG_RTC_DRV_STK17TA8)	+= rtc-stk17ta8.o
 obj-$(CONFIG_RTC_DRV_STMP)	+= rtc-stmp3xxx.o
 obj-$(CONFIG_RTC_DRV_SUN4V)	+= rtc-sun4v.o
+obj-$(CONFIG_RTC_DRV_SUN6I)	+= rtc-sun6i.o
 obj-$(CONFIG_RTC_DRV_SUNXI)	+= rtc-sunxi.o
 obj-$(CONFIG_RTC_DRV_TEGRA)	+= rtc-tegra.o
 obj-$(CONFIG_RTC_DRV_TEST)	+= rtc-test.o