fix: remove RTC clock source selection for Nucleo_F446

This prevents the RTC clock to be reset when clock source is not
the same and a poweroff with VBAT or software reset occurs.
Moreover, LSI does not count when power off and VBAT so it is not
useful.

Fixes #1919

Signed-off-by: Frederic Pillon <[email protected]>

Author: fpistm

variants/STM32F4xx/F446R(C-E)T/variant_NUCLEO_F446RE.cpp

@@ -173,14 +173,13 @@ WEAK void SystemClock_Config(void)
     Error_Handler();
   }
 
-  PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_I2S_APB1 | RCC_PERIPHCLK_RTC;
+  PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_I2S_APB1;
   PeriphClkInitStruct.PLLI2S.PLLI2SN = 192;
   PeriphClkInitStruct.PLLI2S.PLLI2SP = RCC_PLLI2SP_DIV2;
   PeriphClkInitStruct.PLLI2S.PLLI2SM = 16;
   PeriphClkInitStruct.PLLI2S.PLLI2SR = 2;
   PeriphClkInitStruct.PLLI2S.PLLI2SQ = 2;
   PeriphClkInitStruct.PLLI2SDivQ = 1;
-  PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSI;
   PeriphClkInitStruct.I2sApb1ClockSelection = RCC_I2SAPB1CLKSOURCE_PLLI2S;
   if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK) {
     /* Initialization Error */