rtc: add ht1380 driver

Support Holtek HT1380/HT1381 Serial Timekeeper Chip. It provides seconds
, minutes, hours, day of the week, date, month and year information.

Datasheet:
https://www.holtek.com.tw/documents/10179/11842/ht1380_1v130.pdf

Signed-off-by: Sergei Antonov <saproj@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 2089086..acfd130 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -21,6 +21,7 @@
 obj-$(CONFIG_RTC_DS3232) += ds3232.o
 obj-$(CONFIG_RTC_EMULATION) += emul_rtc.o
 obj-$(CONFIG_RTC_FTRTC010) += ftrtc010.o
+obj-$(CONFIG_RTC_HT1380) += ht1380.o
 obj-$(CONFIG_SANDBOX) += i2c_rtc_emul.o
 obj-$(CONFIG_RTC_IMXDI) += imxdi.o
 obj-$(CONFIG_RTC_ISL1208) += isl1208.o