rtc: Add rtc driver for stm32mp1

Add support of STM32MP1 rtc driver.
Enable it for basic and trusted configurations.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 532e94d..0b58a18 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -120,4 +120,10 @@
 	  Enable driver for ST's M41T62 compatible RTC devices (like RV-4162).
 	  It is a serial (I2C) real-time clock (RTC) with alarm.
 
+config RTC_STM32
+	bool "Enable STM32 RTC driver"
+	depends on DM_RTC
+	help
+	  Enable STM32 RTC driver. This driver supports the rtc that is present
+	  on some STM32 SoCs.
 endmenu