rtc: add armada38x driver

Add RTC driver for Armada 38x, based on Linux' driver.
For now implement only `marvell,armada-380-rtc` compatible.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
Cc: Pali Rohár <pali@kernel.org>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: Chris Packham <judge.packham@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Pali Rohár <pali@kernel.org>
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 6a45a9c..15609e7 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -8,6 +8,7 @@
 
 obj-$(CONFIG_RTC_AT91SAM9_RTT) += at91sam9_rtt.o
 obj-y += rtc-lib.o
+obj-$(CONFIG_RTC_ARMADA38X) += armada38x.o
 obj-$(CONFIG_RTC_DAVINCI) += davinci.o
 obj-$(CONFIG_RTC_DS1302) += ds1302.o
 obj-$(CONFIG_RTC_DS1306) += ds1306.o