rtc: zynqmp: Add support for ZynqMP RTC

The whole driver logic is taken from Linux kernel but only set/get/reset
functions are implemented. When device is power off RTC is power out of
battery.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 331a49a..d621be6 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -57,3 +57,4 @@
 obj-$(CONFIG_SANDBOX) += sandbox_rtc.o
 obj-$(CONFIG_RTC_X1205) += x1205.o
 obj-$(CONFIG_RTC_ABX80X) += abx80x.o
+obj-$(CONFIG_RTC_ZYNQMP) += zynqmp_rtc.o