drivers : rtc: clean up usage of "select USE_STM32_LL"

clean up usage of select USE_STM32_LL_RCC and
select USE_STM32_LL_PWR from Kconfig.stm32
this modifications due to the include unconditionally of
stm32xxxx_ll_rcc.h and stm32xxxx_ll_pwr.h in HAL.

Signed-off-by: Khaoula Bidani <khaoula.bidani-ext@st.com>

drivers/rtc/Kconfig.stm32

@@ -6,7 +6,5 @@ config RTC_STM32
 	default y if !COUNTER
 	depends on DT_HAS_ST_STM32_RTC_ENABLED && !SOC_SERIES_STM32F1X
 	select USE_STM32_LL_RTC
-	select USE_STM32_LL_PWR
-	select USE_STM32_LL_RCC
 	help
 	  Build RTC driver for STM32 SoCs, excluding STM32F1 series.