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/MAINTAINERS b/MAINTAINERS
index 776ff70..483a4584 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -600,6 +600,7 @@
 F:	drivers/net/phy/xilinx_phy.c
 F:	drivers/net/zynq_gem.c
 F:	drivers/serial/serial_zynq.c
+F:	drivers/rtc/zynqmp_rtc.c
 F:	drivers/spi/zynq_qspi.c
 F:	drivers/spi/zynq_spi.c
 F:	drivers/timer/cadence-ttc.c