stm32f3: enable RTC

Fixes: https://github.com/libopencm3/libopencm3/issues/1446
Fixes: 18f4d7c1b7 stm32f3: rtc: include correct shared header

No testing on real hardware, but the docs imply that this should have
always had the "basic" rtc-v2 peripheral.

Signed-off-by: Karl Palsson <karlp@tweak.net.au>

include/libopencm3/stm32/f3/rtc.h

@@ -32,8 +32,8 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_RTC_F3_H
-#define LIBOPENCM3_RTC_F3_H
+#ifndef LIBOPENCM3_RTC_H
+#define LIBOPENCM3_RTC_H
 
 #include <libopencm3/stm32/common/rtc_common_l1f024.h>
 

lib/stm32/f3/Makefile

@@ -49,6 +49,7 @@ OBJS += iwdg_common_all.o
 OBJS += opamp_common_all.o opamp_common_v1.o
 OBJS += pwr_common_v1.o
 OBJS += rcc.o rcc_common_all.o
+OBJS += rtc_common_l1f024.o
 OBJS += spi_common_all.o spi_common_v2.o
 OBJS += timer_common_all.o timer_common_f0234.o
 OBJS += usart_common_v2.o usart_common_all.o