stm32f3: rtc: include correct shared header

rtc_common_all never existed, and f3 has the same "v2" peripheral used
by ~all parts other than the f1.  We don't have any f3 rtc test code,
but the existing code was clearly wrong, and this is at least including
the correct basic defines.

Fixes: https://github.com/libopencm3/libopencm3/issues/1106

include/libopencm3/stm32/f3/rtc.h

@@ -34,9 +34,7 @@
 
 #ifndef LIBOPENCM3_RTC_F3_H
 #define LIBOPENCM3_RTC_F3_H
-/**@{*/
 
-#include <libopencm3/stm32/common/rtc_common_all.h>
-/**@}*/
+#include <libopencm3/stm32/common/rtc_common_l1f024.h>
 
 #endif