[RTC] Do not reset RTC Domain

Backup domain is handled by HAL_RCCEx_PeriphCLKConfig() when changing
RTC clock source.
If one other peripheral uses LSE and RTC do not use it, force
reset of the backup domain will break this peripheral.

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/rtc.c

@@ -321,9 +321,6 @@ void RTC_init(hourFormat_t format, sourceClock_t source)
   /* Allow access to Backup domain */
   HAL_PWR_EnableBkUpAccess();
 #endif
-  /* Reset RTC Domain */
-  __HAL_RCC_BACKUPRESET_FORCE();
-  __HAL_RCC_BACKUPRESET_RELEASE();
 
   /* Init RTC clock */
   RTC_initClock(source);