ARM: configs: stm32: Add RTC support in STM32 defconfig

This patch adds STM32 RTC support in stm32_defconfig file.
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>

arch/arm/configs/stm32_defconfig

@@ -56,6 +56,8 @@ CONFIG_LEDS_CLASS=y
 CONFIG_LEDS_GPIO=y
 CONFIG_LEDS_TRIGGERS=y
 CONFIG_LEDS_TRIGGER_HEARTBEAT=y
+CONFIG_RTC_CLASS=y
+CONFIG_RTC_DRV_STM32=y
 CONFIG_DMADEVICES=y
 CONFIG_STM32_DMA=y
 CONFIG_IIO=y