Minor STM32F1 fixes

* Not all STM32 RTCs support subseconds in the time struct, so this is
  now ifdef'd using the only obvious define which exists when subseconds
  exist.
* Let wc_GenerateSeed detect STM32's without RNG correctly.
* wolfCrypt test was attempting to use variables that don't exist when
  both WOLFSSL_SMALL_STACK and WC_NO_RNG is defined.

IDE/STM32Cube/wolfssl_example.c

@@ -1496,12 +1496,15 @@ double current_time(void)
 {
 	RTC_TimeTypeDef time;
 	RTC_DateTypeDef date;
-	uint32_t subsec;
+	uint32_t subsec = 0;
 
 	/* must get time and date here due to STM32 HW bug */
 	HAL_RTC_GetTime(&hrtc, &time, FORMAT_BIN);
 	HAL_RTC_GetDate(&hrtc, &date, FORMAT_BIN);
+	/* Not all STM32 RTCs have subseconds in the struct */
+#ifdef RTC_ALARMSUBSECONDMASK_ALL
 	subsec = (255 - time.SubSeconds) * 1000 / 255;
+#endif
 
 	(void) date;
 

wolfcrypt/src/random.c

@@ -2522,7 +2522,7 @@ int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
 #elif defined(WOLFSSL_SAFERTOS) || defined(WOLFSSL_LEANPSK) || \
       defined(WOLFSSL_IAR_ARM)  || defined(WOLFSSL_MDK_ARM) || \
       defined(WOLFSSL_uITRON4)  || defined(WOLFSSL_uTKERNEL2) || \
-      defined(WOLFSSL_LPC43xx)  || defined(WOLFSSL_STM32F2xx) || \
+      defined(WOLFSSL_LPC43xx)  || defined(NO_STM32_RNG) || \
       defined(MBED)             || defined(WOLFSSL_EMBOS) || \
       defined(WOLFSSL_GENSEED_FORTEST) || defined(WOLFSSL_CHIBIOS) || \
       defined(WOLFSSL_CONTIKI)  || defined(WOLFSSL_AZSPHERE)

wolfcrypt/test/test.c

@@ -16343,7 +16343,7 @@ static int dh_ffdhe_test(WC_RNG *rng, const DhParams* params)
 
 done:
 
-#ifdef WOLFSSL_SMALL_STACK
+#if defined(WOLFSSL_SMALL_STACK) && !defined(WC_NO_RNG)
     if (priv)
         XFREE(priv, HEAP_HINT, DYNAMIC_TYPE_TMP_BUFFER);
     if (pub)