arch/arm/src/: Problem: stm32f30xx hangs waiting for LSE to initialize. Reason for hang is that operation of setting LSE_ON does not take effect because there is no clock on PWR peripheral. this is initialized later in the code

arch/arm/src/stm32/Kconfig

@@ -7365,6 +7365,7 @@ choice
 
 config RTC_LSECLOCK
 	bool "LSE clock"
+	select STM32_PWR
 	---help---
 		Drive the RTC with the LSE clock
 

arch/arm/src/stm32/stm32f30xxx_rcc.c

@@ -660,6 +660,15 @@ static void stm32_stdclockconfig(void)
 #endif
 
 #if defined(CONFIG_RTC_LSECLOCK)
+  /* Normally peripheral clocks are enabled later in bootup, but we need
+   * clock on PWR *now* as without this setting registers that enable LSE
+   * won't work
+   */
+
+  regval  = getreg32(STM32_RCC_APB1ENR);
+  regval |= RCC_APB1ENR_PWREN;
+  putreg32(regval, STM32_RCC_APB1ENR);
+
   /* Low speed external clock source LSE
    *
    * TODO: There is another case where the LSE needs to